Various changes

Languages to use are no longer hardcoded, and should follow parley's preferences.
The input box now follows the practice_text_translation_background element
The prompt text kinda follows the practice_text_background element (this needs work)

The useless eduwidget.h header is now gone.

Themes are now accessed through a .desktop file and are stored in $APPDIR/parley/themes/

TODO: gui fixes, get KNS repo up and working