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/cpptools/cppfindreferences.cpp

@@ -70,6 +70,7 @@
 #include <functional>
 
 using namespace CppTools::Internal;
+using namespace CppTools;
 using namespace CPlusPlus;
 
 static QString getSource(const QString &fileName,