[TASK] Add a .gitignore.

Change-Id: Id6c6c1f055b881fe678130596a25d6d1363e6077
Reviewed-on: http://review.typo3.org/32584
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Tested-by: Oliver Klee <typo3-coding@oliverklee.de>