Button to show *all* known nodes independent of community

[kerlerm]

At the moment, the app only shows nodes of a selected community. But sometimes two or even more different communities offer access in the same area. This is the case in more rural regions, as several bigger city communities are nearby.

As the main purpose of the app is to guide to the nearest available access point, it would be nice to show all nodes in a certain area independent of the community they are connected to!

This ought to be the default setting.