Add Rdio middle-ware source

Original source from Github user tonycosentini
https://github.com/tonycosentini/Rdio-qsplugin/blob/master/RdioSilver/Rdio.h
Add previous Rdio code as a starting point

Source from Github user tonycosentini
https://github.com/tonycosentini/Rdio-qsplugin/tree/master/RdioSilver