Flashlight is not localized

A couple people have expressed interest in translating the Flashlight app and some plugins to their native language (in fact, @xremix has already done German!).

I've written up a document describing how to localize the app and the plugins. If anyone wants to translate anything into their native language, pull requests would be much appreciated!

(there is one small missing technical piece: the web service does not serve localized plugin lists for browsing. I'll fix this as soon as I have time.)