[RELEASE] Release of TYPO3 6.1.0alpha1

Change-Id: If1bbb1fab9f79ddfab6c848c6549d9244cfc6f98
Reviewed-on: https://review.typo3.org/18865
Reviewed-by: TYPO3 Release Team
Tested-by: TYPO3 Release Team
[TASK] Set TYPO3 version to 6.1-dev

Change-Id: Ic7f565cb3188194e47a13b284a9d5f79e90d8616
Reviewed-on: https://review.typo3.org/18866
Reviewed-by: TYPO3 Release Team
Tested-by: TYPO3 Release Team