qml: moving most of ModelManager logic to ModelManageInterface

Currently ModelManager contains lot logic, but as it sits in QmlJSTools
it is not possible to use it in standalone tests.
Moving most of the logic to ModelManagerInterface (and cleanup)
to allow better testing, and refactoring.
This introduces a dependency of the qmljs lib on the cplusplus lib
Also a (small) part of the CppTool::ModelManagerInterface has been
moved to CPlusPlus::CppModelManagerBase to remove the dependency on
CppTools to gather the Qml types exposed from C++.

Change-Id: Icad7fe96dfd0f1a2b1058d82bd98c77c40aa5e9d
Reviewed-by: Fawzi Mohamed <fawzi.mohamed@digia.com>