Consider other map sources

[Simoma]

Consider changing default map from openstreetmap.org to something else, perhaps MapQuest Open. This avoids load on openstreetmap.org.
Consider adding possibility to select from few map sources.

[otsaloma]

This should be doable, to some extent, with changes in the osm plugin in QtLocation 5.6, if we ever get that upgrade in SFOS. There's also a Mapbox plugin added. With the current QtLocation 5.2, you'd probably need to write a custom plugin, which is likely more trouble that it's worth.

• https://bugreports.qt.io/browse/QTBUG-32937

• http://doc.qt.io/qt-5.6/location-plugin-osm.html (parameter osm.mapping.custom.host)

• http://doc.qt.io/qt-5.6/location-plugin-mapbox.html