CppEditor: Pimpl CppEditorWidget

...to cut some build depedencies.

Change-Id: I11b7e5f3c12b6821d0825a94ad74a7e4b69c4b12
Reviewed-by: Erik Verbruggen <erik.verbruggen@digia.com>
CppEditor: Further cleanup

* Kill duplicate code
* Kill useless forwarding function
* Regroup some declarations
* Replace include by declaration

Change-Id: I54656e4e97b1fbdf7cf2f4a87d17955128f3825e
Reviewed-by: Erik Verbruggen <erik.verbruggen@digia.com>
CppEditor: Use BaseTextEditor{Widget} if possible

Change-Id: I59c420c6469717e552469d176bbeac3a455f3bb0
Reviewed-by: Erik Verbruggen <erik.verbruggen@digia.com>
Make document model API more consistent with entry vs document

Change-Id: Iae2fe480d9fcb564d566f1dcca142c21c99c2d5b
Reviewed-by: hjk <hjk121@nokiamail.com>