0024784: Move documentation in CDL files to proper location

Mostly duplicated comments were removed and missing ones were moved
into dedicated class CDL files.
Some more duplicated comments were removed from CDL files.
Correction of merge

src/STEPConstruct/STEPConstruct.cdl

@@ -45,32 +45,23 @@ uses
 is
 
     class Tool;
-    	---Purpose: Basic class providing general features
-	
+
     class UnitContext;
-    	---Purpose: Create and investigate context of units and uncertanties
 
     class Part;
-    	---Purpose: Create and investigate data associated with parts (product etc.)
-	
+
     class Assembly;
-    	---Purpose: Create and check assembly data structures
-    
+
     class Styles;
-    	---Purpose: Create and investigate STEP constructs for styles (mostly colors)
-    
+
     class ValidationProps;
-    	---Purpose: Create and investigate STEP constructs for validation properties
-    
+
     class ExternRefs;
-    	---Purpose: Work with references to external documents
-    
+
     class AP203Context;
-        ---Purpose: maintains context specific to AP203
-    
+
     class ContextTool;
-        ---Purpose: Maintains global context tool for writing
-	
+
     --- skl 15.01.2004
     class DataMapOfAsciiStringTransient instantiates 
     	  DataMap from TCollection (AsciiString from TCollection,

src/STEPConstruct/STEPConstruct_Assembly.cdl

@@ -16,7 +16,7 @@
 
 class Assembly  from STEPConstruct
 
-    ---Purpose : This operator creates an item of an assembly, from its
+    ---Purpose : This operator creates and checks an item of an assembly, from its
     --           basic data : a ShapeRepresentation, a Location ...
     --           
     --           Three ways of coding such item from a ShapeRepresentation :

src/STEPConstruct/STEPConstruct_ContextTool.cdl

@@ -16,7 +16,8 @@
 
 class ContextTool from STEPConstruct
 
-    ---Purpose : Gives access to Product Definition Context (one per Model)
+    ---Purpose : Maintains global context tool for writing.
+    --           Gives access to Product Definition Context (one per Model)
     --           Maintains ApplicationProtocolDefinition entity (common for all
     --           products)
     --           Also maintains context specific for AP203 and provides set of