Sort out usage of INset::has Settings and Inset::clickable

Sort out usage of INset::has Settings and Inset::clickable

 * now hasSettings only means... that the inset has a settings dialog
 * and clickable means that something should happen with left-clicking on the inset

Some inset behaviours are changed:
 * (V)Space insets are not clickable anymore (the settings dialog is still accessible via context menu and Edit menu)
 * TOC inset is now shown as active
 * FloatList inset is shown as active and clicking on it opens the relevant part of the TOC dialog

This could be a candidate for branch (2.0.4)

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@40755 a592a061-630c-0410-9148-cb99ea01b6c8