[BUGFIX] Show correct tooltip for page type "Mount Point"

The tooltip of pages of the type "Mount Point" lacks the information
about the linked page because the needed fields are not retrieved.

Additionally the shortcut tooltip gets improved for the page tree.

Change-Id: I9c7c65094d23bbc0b0eb6100b0d6a62641c00d22
Resolves: #61951
Related: #60033
Releases: master, 6.2
Reviewed-on: http://review.typo3.org/33180
Reviewed-by: Stefan Froemken <froemken@gmail.com>
Tested-by: Stefan Froemken <froemken@gmail.com>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>