Light sensor cleanup

Connects the light sensor to the timeout and startup preferences.
Also, some cleanup of the light sensor UI.
# Please enter the commit message for your changes. Lines starting
# with '#' will be ignored, and an empty message aborts the commit.
# On branch master
# Your branch is up-to-date with 'origin/master'.
#
# Changes to be committed:
#	modified:   doc/about.html
#	modified:   lanlightsensorform.cpp
#	modified:   lanlightsensorform.h
#	modified:   lanlightsensorform.ui
#	modified:   lanpreferencesform.cpp
#	modified:   lanpreferencesform.h
#	modified:   mainwindow.cpp
#	modified:   mainwindow.h
#	modified:   qtc_packaging/debian_fremantle/changelog
#	modified:   qtc_packaging/debian_fremantle/control
#
# Untracked files:
#	lanlightsensorform.ui.autosave
#	lanterne.pro.user
#
