Use forward_key_event instead of commit_text in Gtk apps

We have to forward each character instead of committing them
because of a synchronization issue in Gtk/IBus
where sometimes, the committed text comes before the forwarded
backspaces, resulting in undesirable output.

Should satisfy bug #20.
Don't do skip-non-vietnamese by default
No shebang in lib files
Minor fixes

- fix BoGo icon's name when run locally
- Add a do_reset handler
- add TODO in keysyms_mapping.py