[TASK] Fix CGL violations against DoubleQuoteUsage

Some violations against other CGL rules have been fixed as well.

Change-Id: I952218d140f559d0d90d4fc070f8de5820134461
Resolves: #38027
Releases: 6.0
Reviewed-on: http://review.typo3.org/12041
Reviewed-by: Xavier Perseguers
Tested-by: Xavier Perseguers
Reviewed-by: Oliver Klee
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn