Removed cotire PCH
Integrated native PCH by CMake with the same BUILD_USE_PCH flag
Added new option to avoid extra files in 'build/include' folder and replace it by symlink
Symlink creates link to the origin file, it has some benefits from debug and build side.
The CMake parameter for symlink is 'BUILD_INCLUDE_SYMLINK'
Moved ExpToCasExe and its DLL to new module - DETools
Created new module - DETools to keep tools to DE
Changed definition of main of ExpToCasExe to not const parameter
FlexLexer.h moved to general location into TKernel
Possibility for adding LengthUnit info to XCAF document using special class XCAFDoc_LenghtUnit and XCAFDoc_LenghtUnitTool is implemented.
Package UnitsMethods is split: geom methods were placed to new file GeomConvert_Units which is in the toolkit TKXSBase, internal step scale factors was placed to StepData.
Updated UnitMethods to convert scale factor to different unit types.
Now, XSAlgo::XSAlgo_AlgoContainer is used to update unit info from static interface values.
New Draw command "XSetLengthUnit" and "XGetLengthUnit" for set or get XDE attribute.
Upgraded tests for STEP, IGES, OBJ, glTF, VRML formats to check area regressing with used unit.
Upgraded tests\de test cases to use any units in the "loop back" algorithms.
Class Dico_Dictionary was replaced by NCollection_DataMap/NCollection_IndexedDataMap classes.
Changed argument name in template class NCollection_Datamap to eliminate redefinitions of static members in dependent code.
Package SortTools and its derived classes are removed; STL sort algorithms are used instead.
Comparator objects are mostly reimplemented as local classes.
