String tweaks:
* Empty pane message: say "pane" instead of "view", and say "open" instead
of "select" (to reduce the confusion in #9254)
* JS File Inference Problem dialog: ask users to file a Brackets bug; fix
capitalization; format more like other errors that call out a filename.
* Remove unused UNSUPPORTED_FILETYPE error & its corresponding string (I
think this was leftover from an earlier part of splitview)
Code review: Update link in JS code hints error dialog
Merge pull request #9280 from adobe/pflynn/string-tweaks

String tweaks