[RELEASE] Release of TYPO3 4.7.8

Change-Id: I07c656128526f83370b4367cdbe0464320e211d1
Reviewed-on: https://review.typo3.org/18281
Reviewed-by: TYPO3 Release Team
Tested-by: TYPO3 Release Team
[TASK] Set TYPO3 version to 4.7.9-dev

Change-Id: Ic20868edbff51340ce73365fad947e49035e12f0
Reviewed-on: https://review.typo3.org/18282
Reviewed-by: TYPO3 Release Team
Tested-by: TYPO3 Release Team