0025418: Debug output to be limited to OCC development environment

Macros ending on "DEB" are replaced by OCCT_DEBUG across OCCT code; new macros described in documentation.
Macros starting with DEB are changed to start with "OCCT_DEBUG_".
Some code cleaned.

src/FEmTool/FEmTool_Assembly.cxx

@@ -200,7 +200,7 @@ Standard_Boolean FEmTool_Assembly::Solve()
 {
   IsSolved = H->Decompose();
 
-#if FEMTOOL_DEB
+#ifdef OCCT_DEBUG
   if (!IsSolved) {
     cout << "Solve Echec  H = " << endl;
     H->OutM();