[BUGFIX] Select correct module in User Settings

If the first entry of the select box is chosen (option has an
empty value), this selection is preserved now after saving the form.

Additionally the empty value given a proper label to describe its
functionality.

The rendering is adjusted to use optgroup-elements now.

Resolves: #66893
Releases: master
Change-Id: Ic6a77086a86d353075dc771a23df74617697f01e
Reviewed-on: http://review.typo3.org/39465


Reviewed-by: Frederic Gaus <frederic.gaus@flagbit.de>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Xavier Perseguers <xavier@typo3.org>
Tested-by: Xavier Perseguers <xavier@typo3.org>