485 default layers

Closes #485.
Layers included:
 * Ona Default (Mapbox Terrain)
 * Mapbox Satellite
 * [Ona Plain](https://a.tiles.mapbox.com/v4/ona.jjoa711a/page.html?access_token=pk.eyJ1Ijoib25hIiwiYSI6IlVYbkdyclkifQ.0Bz-QOOXZZK01dq4MuMImQ#0/-36/27).
 * Google Satellite