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/abstracteditorsupport.cpp

@@ -45,8 +45,6 @@
 
 #include <QDebug>
 
-using namespace CPlusPlus;
-
 namespace CppTools {
 
 AbstractEditorSupport::AbstractEditorSupport(CppModelManagerInterface *modelmanager) :
@@ -97,5 +95,6 @@ QString AbstractEditorSupport::licenseTemplate(const QString &file, const QStrin
 {
     return Internal::CppFileSettings::licenseTemplate(file, className);
 }
-}
+
+} // namespace CppTools