Fixes to comment based on cursor pos

Identify CSS <style> blocks
Only if we didn't identify caretLocType and have a fileName do we go by
file extension
Esc falls through to ICEcoder control now

If we have multiple selections, deselect to the primary selection only.
If we only have a single selection, then we comment/uncomment.

(Avoids having multiple selections, pressing Esc to clear to a single
and also unwantedly commenting/uncommenting).