Refactoring/restructuring

 The two drivers are coalesced into one, you choose between mplayer
 and vlc with a commandline option. driver_common is history, its
 functionality is now all either back in the unified driver or in
 parse_iheart_json. A few minor changes applied along the way -
 for instance, now standardized on double quotes for UI strings
 and single quotes for all other strings.