CppTools: Use namespace CppTools consistently

There were quite a few classes using CPlusPlus namespace in the
CppTools plugin. Rename them and do some other small namespace
related coding style fixups.

Change-Id: I093fc1f3fc394fd9923e3f18d5f66522e288f21d
Reviewed-by: Erik Verbruggen <erik.verbruggen@digia.com>

src/plugins/cppeditor/cppelementevaluator.h

@@ -49,9 +49,7 @@ class LookupItem;
 class LookupContext;
 }
 
-namespace CppTools {
-class CppModelManagerInterface;
-}
+namespace CppTools { class CppModelManagerInterface; }
 
 namespace CppEditor {
 namespace Internal {
@@ -84,7 +82,7 @@ private:
                                const CPlusPlus::LookupContext &lookupContext);
 
     CPPEditorWidget *m_editor;
-    CPlusPlus::CppModelManagerInterface *m_modelManager;
+    CppTools::CppModelManagerInterface *m_modelManager;
     QTextCursor m_tc;
     bool m_lookupBaseClasses;
     bool m_lookupDerivedClasses;