[BUGFIX] Make FAL work in the flexform field having dot in the name

Fixes regression introduced in I6599c3ce7eea493e2bfaa29312775bf1659ded69
During the change from prototype to jQuery few places missed
escaping of the dot in the id of the DOM node.

This patch fixes these places and also few other jQuery related bugs
E.g. we have to use "object.length" to test if jQuery selector
was found.

Resolves: #62001
Related: #58475
Releases: master
Change-Id: I9bb661c5bf58aa9b73106a1e48f2206465a8974e
Reviewed-on: http://review.typo3.org/33106
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Markus Klein <klein.t3@reelworx.at>
Tested-by: Markus Klein <klein.t3@reelworx.at>