[RELEASE] Release of TYPO3 4.7.12

Change-Id: I22af02565b483495de0d99044d2dc20e2e387c14
Reviewed-on: https://review.typo3.org/21028
Reviewed-by: TYPO3 Release Team
Tested-by: TYPO3 Release Team
[TASK] Set TYPO3 version to 4.7.13-dev

Change-Id: I0541ac94efef7077bf66e9b86381d27488b97c1c
Reviewed-on: https://review.typo3.org/21029
Reviewed-by: TYPO3 Release Team
Tested-by: TYPO3 Release Team