conform gui to concerto

This change includes not only making it fit into concerto's gui style (helping with #1), but also includes some localization, removes some debug code and places the config item on the "system" tab.

To test this, make sure that you have this PR from concerto applied so the player details show up nicely in a sidebar on concerto's screen#show-- https://github.com/concerto/concerto/pull/781