SongIdNotifier: refactored
-most attributes are now non-const and can be altered after class
 creation
Config
class parsing and saving the entire configuration
-uses boost::program_options for parsing
-includes print function for available MIDI devices (and their IDs)
-allows loading of a response file with more configuration options
-main.cpp contains the extended test program
-Makefile: link boost libraries and portmidi library
StatusExchange
class to exchange information between the XMMS2 client and the MIDI
master
-exchanged information:
    * playback status
    * time
    * song id
-thread safety: provided by usage; no mutex required yet