CDU: Map tile data providers

[SammySkycrafts]

Stamen recently killed their maptile service on the 31st October, moving to a paid model. The CDU uses 2 services from Stamen for Windows and Linux users (macOS don't have these because of the issue where they stayed in B&W) - This will affect the CDU and cause no tiles to be rendered.

Ideally, we would want to find alternative providers. In the mean time, we could remove the STAMEN services from the CDU, and leave the remaining service. Or maybe add a service like OSM instead of satellite or terrain-based maps.

[NikolaiVChr]

In commit 7a9f023 I changed Stamen for Acrgis topo.

Am leaving this issue open, since we might want to add more providers.

[NikolaiVChr]

VFR for US added