[TASK] Migrate EXT:about to extbase

Change-Id: If4161ce96038778776bcc654ad8a09b550568d44
Resolves: #34096
Releases: 4.7
Reviewed-on: http://review.typo3.org/9104
Reviewed-by: Philipp Gampe
Tested-by: Philipp Gampe
Reviewed-by: Steffen Ritter
Tested-by: Steffen Ritter
Reviewed-by: Tolleiv Nietsch
Tested-by: Tolleiv Nietsch