[TASK] Add a .gitignore.

Change-Id: I46fc4bc7d8a091efcabe13bd3ac5b3e8bc36b4ea
Reviewed-on: http://review.typo3.org/32585
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Tested-by: Oliver Klee <typo3-coding@oliverklee.de>