Editor code: tidy up BOOLs,NULLs and overrides pt1.

A few 'typedefs' replaced by 'using's
This shouldn't have any functional changes at all, just c++17 modernization
It's a part 1 of a split #2847

Signed-off-by: Nemerle <nemerle5+git@gmail.com>

Code/Editor/Export/OBJExporter.cpp

@@ -67,7 +67,7 @@ bool COBJExporter::ExportToFile(const char* filename, const Export::IData* pExpo
         while (nParent >= 0 && nParent < pExportData->GetObjectCount())
         {
             const Export::Object* pParentObj = pExportData->GetObject(nParent);
-            assert(NULL != pParentObj);
+            assert(nullptr != pParentObj);
 
             Vec3 pos2(pParentObj->pos.x, pParentObj->pos.y, pParentObj->pos.z);
             Quat rot2(pParentObj->rot.w, pParentObj->rot.v.x, pParentObj->rot.v.y, pParentObj->rot.v.z);