Option to backup/restore app data to dropbox, drive, etc

[rejhgadellaa]

Related to issue #180

The easy part is the data that is already stored on local storage (stations,json, session.json, etc) so that can be exported without too much hassle. It's probably already possible to restore those files after a fresh install (< try this out, it's basically the manual version of what needs automation) and have Icerrr work with those.

What does need looking at is what's stored in the app's SharedPreferences. I don't think it's vital stuff but it might need some extra care to restore the data and send all required data to the java part of things.

[rejhgadellaa]

Just tried replacing data on storage (Icerrr/*) with backup. Stations data probably works but session is loaded from cookie (and only if that fails it loads from storage). So I need to do something there..