The added provider is selected automatically.

I've also removed a lot of finishes when things go wrong (so that it should be returning to the previous activity/fragment).
Changed user message when a provider is down.

I was assuming that if the app wasn't able to download provider.json from the web, it meant that the preseeded provider was wrong thus the app needed an upgrade. But it can happen (as right now, with bitmask.net) that the provider is simply down.