[TASK] Make extbase and fluid required extensions

Change-Id: I5a835a27b7f4e2a2301365b5c61aece765c564aa
Resolves: #20634
Releases: 6.0
Reviewed-on: http://review.typo3.org/10243
Reviewed-by: Wouter Wolters
Reviewed-by: Rens Admiraal
Reviewed-by: Andy Grunwald
Tested-by: Andy Grunwald
Reviewed-by: Andreas Wolf
Tested-by: Andreas Wolf