Fix issue #2: FPaths::ConvertRelativePathToFull(*File)

 - fix build error (missing parenthesis).
Look for the Git root directory in Init()

 - fix a small issue with the first "UpdateStates" issued before the "Connect" command
The Git Plugin does not uses the "CheckOut" command

 - it as not the same meaning as Perforce, where it is a "lock" command:
   this does not exists in Git