[BUGFIX] clickenlarge not working on images inserted by FAL-enabled RTE

Solution: Get original file from data-htmlarea-file-uid attribute

Change-Id: I5c4aef33bdcbe7c5badac9173480e33fb627b302
Releases: 6.0
Resolves: #36718
Reviewed-on: http://review.typo3.org/10894
Reviewed-by: Stanislas Rolland
Tested-by: Stanislas Rolland