[TASK] Add a .gitignore.

Change-Id: I6f0e8c59145627b8cee9d5edb7faa8892c925781
Reviewed-on: http://review.typo3.org/32587
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Tested-by: Oliver Klee <typo3-coding@oliverklee.de>