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.

This is in anticipation of a change in the next gdb release
which will drop the token.

Details:  Found while reading the code. It was only used in that
function anyway, and this simplfies the code a little bit and
removes some dubious left over.

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:     Reported by eskil on irc.

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