[BUGFIX] Trigger inline editing only for page title

The page title now has a t3js prefixed class to make sure only
this <h1> is editable, and not every <h1> that may occurs, e.g.
in a preview of a content element in the Page module.
Additionally, only the first found element is used.

Resolves: #69600
Releases: master
Change-Id: I17ba4180cb8f71504e5097b8a6b42c4884e46b2b
Reviewed-on: http://review.typo3.org/43158


Reviewed-by: Alexander Opitz <opitz.alexander@googlemail.com>
Tested-by: Alexander Opitz <opitz.alexander@googlemail.com>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>