[TASK] Set TYPO3 version to 7.1.0-dev

Resolves: #63547
Releases: master
Change-Id: I8f48df6de186b416e6a960e8f176afddabb5614d
Reviewed-on: http://review.typo3.org/34971
Reviewed-by: Sebastian Michaelsen <michaelsen@t3seo.de>
Tested-by: Sebastian Michaelsen <michaelsen@t3seo.de>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>