Inspector line cleanup

The first commit fixes the actual bug in http://musescore.org/en/node/36446.  I didn't change the basic design of greying out STYLED properties, although that could be worth further discussion in http://musescore.org/en/node/36451.

The second commit just does a bit of cleanup on something that has long bugged me - the empty "Text Line" group in the Inspector for text lines (including pedal, ottava, and volta).  I didn't remove the source file for that control; I just commented out the places where it was referenced.  So if we do ever decide to populate that group (we could have begin / continue / end text styles, for instance), it would be easy enough to add it back.