Cache map data

[tomrijnbeek]

There should be a system that puts the JSON and map image in a local file after downloading it form the service, so that the data doesn't have to be downloaded again. The map loading should then be done locally if possible.

There should probably also be a system that makes sure the local and remote versions are identical, but that is less of a priority.

[Mattias1]

The system that makes sure the local and remote are the same can be a button that removes the current one and fetches the new one - that works and is easy enough to do.