[RELEASE] Release of TYPO3 4.6.17

Change-Id: I257db407a3a3c6f058c67eb1caf82702f32b4004
Reviewed-on: https://review.typo3.org/18743
Reviewed-by: TYPO3 Release Team
Tested-by: TYPO3 Release Team
[TASK] Set TYPO3 version to 4.6.18-dev

Change-Id: I6fbdee5980c7e84242c84157be61f091b2495da5
Reviewed-on: https://review.typo3.org/18744
Reviewed-by: TYPO3 Release Team
Tested-by: TYPO3 Release Team