[BUGFIX] Wrong placement of image caption in text with image

If you omit the first caption, then the following captions are shifted
into this position, meaning the the captions are off by the number of
empty captions in front.

This happens because the captions are stored with a newline "\n" as
separator which is removed by a trim = 1.

Remove this trim from tt_content.image.20.caption.1.1 as the trimming of
the actual content happens with
tt_content.image.20.caption.1.stdWrap.trim = 1.

The change also has a few cleanups that popped up in PhpStorm while
investigation the issue.

Resolves: #48354
Releases: 6.2, 6.1, 6.0
Change-Id: I4523fa40cbf991b3941d18145a09e72d5e5254d3
Reviewed-on: https://review.typo3.org/20884
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters
Reviewed-by: Stefan Neufeind
Tested-by: Stefan Neufeind