[TASK] Add a .gitignore.

Change-Id: Ie486dfa6242ef80de15a9d53d996ade6e1dc146d
Reviewed-on: http://review.typo3.org/32586
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Tested-by: Oliver Klee <typo3-coding@oliverklee.de>