Details:  - Conform to conventions.

Details:  - To make it conform to naming convention.

Details:  - Step one, step two is ActionManagerInterface -->
ActionManager because it conflicts with our naming conventions

Fixes: Random enabling of submit/diff buttons when switching contexts (viewing diffs) from the submit editor

Details: Register actions directly

It didn't make sure its Function* stayed valid. Now it does, by keeping
a copy of the list of CppDocuments (the snapshot) around.

(makes standard key bindings work)

Fixes: Make git diff work for staged files, do not launch submit if file list empty, make file  model read only, add conveniences

Details: Add a type data field to the git file model

Details:  Copy and paste error

Not entirely sure about the location of the menu entry. Also, the dialog
is in dire need of a redesign.

Details:  One step at a time.