[BUGFIX] Adjust shortcut mode labels for selected/current page

If a certain page is selected then shortcut mode refers to that page.
Only otherwise the current page is the point of reference for
first/random/parent.

Change-Id: I2d765665b1ee73a410e1b6fe8a619833b6850476
Resolves: #26690
Releases: 4.7, 4.6
Reviewed-on: http://review.typo3.org/2790
Reviewed-by: Oliver Hader
Tested-by: Oliver Hader
Reviewed-by: Markus Klein
Tested-by: Markus Klein
Reviewed-by: Philipp Gampe
Tested-by: Philipp Gampe
Reviewed-by: Steffen Gebert
Tested-by: Steffen Gebert