Refactor application into data sources that can return data headlessly

[v79]

Each data source (spotify, google calendar...) should be able to run and return data without calling or displaying anything on the screen. That way, I can ease debugging of data fetching without the slowness of the screen refreshes.

Define a communications format so that the data source can provide instructions to the display routine? Perhaps something in JSON?

{ "black": {
  "lg-w": "This is my song title",
   "sm-t": "Album name"
  },
  "red": {
 "sm-t": "Singer name",
  }
}

This might be OK for text, but will be much harder to send draw commands?