Details: Refactor the git command to be able to run a batch. Run diff and diff --cached in a batch

The previous interface wasn't sufficient to properly support the Apply
button, since it didn't separate applying the changes from the cleanup
phase.

Designer settings pages still need some fixing.

Fixes Apply button causing problems for certain plugins, for example the
QuickOpen.

Details:  - Conform to conventions.

Details:  - To make it conform to naming convention.

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

Details: Register actions directly

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: Move routine to get project file list into VCSBase, use it in p4 and git to filter submit lists.

Task:
RevBy:
AutoTest:
Details: Moved code to create a local branch from model to dialog which is slightly better since all the modifying app code is there.

Task: 205821
Details: Split up the branch model into remote branch base class and extended local branch class with <New Branch> row.

Details:  in all pluginspecs.

Now it uses all the available space.

Task:     - 237689
Details:  - .git is a hidden file, so we need the QDir::Hidden flag as well

Details: Execute git status from repo directory

Task: 205821
RevBy: con
Details:  Add a IVersionControl to git. Extend IF to able to return a name and add enabling options. Connect project explorer to enable the right VCS.

Task: 205821
RevBy: Eike
Details: Add a IVersionControl to git. Extend IF to able to return a name and add enabling options. Connect project explorer to enable the right VCS.

With many git commands it is safer to disambiguate files from refs by
putting '--' in front of the list of files.

Also corrected a margin in the git submit panel.

Task:     -
RevBy:    -
AutoTest: -
Details:  -