[TASK] Version Bump 1.2.0-dev

Releases: 6.1, 4.7, 4.5
Change-Id: Ie8446316bc8c70e473935db83c2f5ce9441cdafc
Reviewed-on: https://review.typo3.org/29062
Reviewed-by: Ralf Zimmermann
Tested-by: Ralf Zimmermann