[TASK] Set TYPO3 version to 6.2.8-dev

Change-Id: Ia4316d5ad5d06f4eb62d309a59954d334c73573a
Reviewed-on: http://review.typo3.org/34684
Reviewed-by: TYPO3 Release Team <typo3v4@typo3.org>
Tested-by: TYPO3 Release Team <typo3v4@typo3.org>