[TASK] Add plugin name to page module's CE

During cleanup of the page module's CE rendering
a bit too much cleanup happened and the name
of the plugin is not shown anymore. Furthermore "No
plugin is selected" is now shown if nothing yet selected

Change-Id: I3b2210eca870f3c4f2ed059cf6f80f63dc6416d2
Resolves: #37944
Relases: 6.0
Reviewed-on: http://review.typo3.org/11975
Reviewed-by: Mattias Nilsson
Tested-by: Mattias Nilsson
Reviewed-by: Philipp Gampe
Tested-by: Philipp Gampe
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters
Reviewed-by: Georg Ringer
Tested-by: Georg Ringer