BaseTools: add script to configure local git options

Patch contribution and review is greatly simplified by following the
steps described in "Laszlo's unkempt guide":
https://github.com/tianocore/tianocore.github.io/wiki/Laszlo's-unkempt-git-guide-for-edk2-contributors-and-maintainers
but there are a lot of tedious manual steps in there, so here is a
python script that configures all options I am aware of
*for the repository the script is executed from*.

Signed-off-by: Leif Lindholm <leif.lindholm@linaro.org>
Acked-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Bob Feng <bob.c.feng@intel.com>