Add some magit integration

[hanfried]

The non-interactive detection does not work when called from emacs magit. Also we'd like to force git-good-commit to commit a message, like when doing interactive.

So added logic to detect whether we are inside emacs and that looks in the comment section of the commit message if there is somewhere a

   # ggc: y

defined as comment and if, then it commits anyway. Otherwise it exits with an error message and also explaining what to do in case of forcing the commit.