0026106: BRepMesh - revision of data model

Removed tight connections between data structures, auxiliary tools and algorithms in order to create extensible solution, easy for maintenance and improvements;
Code is separated on several functional units responsible for specific operation for the sake of simplification of debugging and readability;
Introduced new data structures enabling possibility to manipulate discrete model of particular entity (edge, wire, face) in order to perform computations locally instead of processing an entire model.

The workflow of updated component can be divided on six parts:
* Creation of model data structure: source TopoDS_Shape passed to algorithm is analyzed and exploded on faces and edges. For each topological entity corresponding reflection is created in data model. Note that underlying algorithms use data model as input and access it via common interface which allows user to create custom data model with necessary dependencies between particular entities;
* Discretize edges 3D & 2D curves: 3D curve as well as associated set of 2D curves of each model edge is discretized in order to create coherent skeleton used as a base in faces meshing process. In case if some edge of source shape already contains polygonal data which suites specified parameters, it is extracted from shape and stored to the model as is. Each edge is processed separately, adjacency is not taken into account;
* Heal discrete model: source TopoDS_Shape can contain problems, such as open-wire or self-intersections, introduced during design, exchange or modification of model. In addition, some problems like self-intersections can be introduced by roughly discretized edges. This stage is responsible for analysis of discrete model in order to detect and repair faced problems or refuse model’s part for further processing in case if problem cannot be solved;
* Preprocess discrete model: defines actions specific for implemented approach to be performed before meshing of faces. By default, iterates over model faces and checks consistency of existing triangulations. Cleans topological faces and its adjacent edges from polygonal data in case of inconsistency or marks face of discrete model as not required for computation;
* Discretize faces: represents core part performing mesh generation for particular face based on 2D discrete data related to processing face. Caches polygonal data associated with face’s edges in data model for further processing and stores generated mesh to TopoDS_Face;
* Postprocess discrete model: defines actions specific for implemented approach to be performed after meshing of faces. By default, stores polygonal data obtained on previous stage to TopoDS_Edge objects of source model.

Component is now spread over IMeshData, IMeshTools, BRepMeshData and BRepMesh units.

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1. Extend "tricheck" DRAW-command in order to find degenerated triangles.

2. Class BRepMesh_FastDiscret::Parameters has been declared as deprecated.

3. NURBS range splitter: do not split intervals without necessity. Intervals are split only in case if it is impossible to compute normals directly on intervals.

4. Default value of IMeshTools_Parameters::MinSize has been changed. New value is equal to 0.1*Deflection.

5. Correction of test scripts:

1) perf mesh bug27119: requested deflection is increased from 1e-6 to 1e-5 to keep reasonable performance (but still reproducing original issue)
2) bugs mesh bug26692_1, 2: make snapshot of triangulation instead of wireframe (irrelevant)

Correction in upgrade guide.

dox/dev_guides/upgrade/upgrade.md

@@ -1627,3 +1627,48 @@ Now methods *GeomConvert::ConcatG1*, *GeomConvert::ConcatC1*, *Geom2dConvert::Co
 Previously Document format version after restoring by DocumentRetrievalDriver was propagated using static methods of corresponding units (like MDataStd or MNaming) to static variables of these units and after that became accessible to Drivers of these units.
 Now Document format version is available to drivers via RelocationTable. The Relocation table now keeps HeaderData of the document and a format version can be extracted in next way: theRelocTable.GetHeaderData()->StorageVersion().
 Obsolete methods: *static void SetDocumentVersion (const Standard_Integer DocVersion)* and *static Standard_Integer DocumentVersion()* of *BinMDataStd*, *BinMNaming*, *XmlMDataStd* and *XmlMNaming* are removed.
+
+@subsection upgrade_740_changed_api_of_brepmesh BRepMesh - revision of the data model
+
+The entire structure of *BRepMesh* component has been revised and separated into several logically connected classes.
+
+In new version, deflection is controlled more accurately, this may be necessary to tune parameters of call of the BRepMesh algorithm on the application side to obtain the same quality of presentation and/or performance as before.
+
+*BRepMesh_FastDiscret* and *BRepMesh_FastDiscretFace* classes have been removed.
+
+The following changes have been introduced in the API of *BRepMesh_IncrementalMesh*, component entry point:
+* Due to revised logic, *adaptiveMin* parameter of the constructor has been removed as meaningless;
+* *BRepMesh_FastDiscret::Parameters* has been moved to a separate structure called *IMeshTools_Parameters*; the signatures of related methods have been changed correspondingly.
+
+* Interface of *BRepMesh_Delaun* class has been changed.
+
+Example of usage:
+Case 1 (explicit parameters):
+~~~~
+#include <IMeshData_Status.hxx>
+#include <IMeshTools_Parameters.hxx>
+#include <BRepMesh_IncrementalMesh.hxx>
+
+Standard_Boolean meshing_explicit_parameters()
+{
+  BRepMesh_IncrementalMesh aMesher (aShape, 0.1, Standard_False, 0.5, Standard_True);
+  const Standard_Integer aStatus = aMesher.GetStatusFlags();
+  return !aStatus;
+}
+
+Standard_Boolean meshing_new()
+{
+  IMeshTools_Parameters aMeshParams;
+  aMeshParams.Deflection               = 0.1;
+  aMeshParams.Angle                    = 0.5;
+  aMeshParams.Relative                 = Standard_False;
+  aMeshParams.InParallel               = Standard_True;
+  aMeshParams.MinSize                  = Precision::Confusion();
+  aMeshParams.InternalVerticesMode     = Standard_True;
+  aMeshParams.ControlSurfaceDeflection = Standard_True;
+
+  BRepMesh_IncrementalMesh aMesher (aShape, aMeshParams);
+  const Standard_Integer aStatus = aMesher.GetStatusFlags();
+  return !aStatus;
+}
+~~~~