[TASK] Set TYPO3 version to 6.2.7-dev

Change-Id: If7d07a856f639be00c5e15f5fbdee3096fc178dc
Reviewed-on: http://review.typo3.org/33468
Reviewed-by: TYPO3 Release Team <typo3v4@typo3.org>
Tested-by: TYPO3 Release Team <typo3v4@typo3.org>