[RELEASE] Release of TYPO3 6.1.0beta1

Change-Id: I9efec045bc2fe250039fed3aae136cdf0cf8c23b
Reviewed-on: https://review.typo3.org/19537
Reviewed-by: TYPO3 Release Team
Tested-by: TYPO3 Release Team
[TASK] Set TYPO3 version to 6.1-dev

Change-Id: I260f2e8e105e76485247a8e5ce0abce641618be7
Reviewed-on: https://review.typo3.org/19538
Reviewed-by: TYPO3 Release Team
Tested-by: TYPO3 Release Team