Scrolling through large lists was a pain. The next page would only load
when the end of the list was reached, stopping the scroll action while the new
page was fetched.
This commits adds two items:
* Artists, albums and playlists do not refresh data on resume, only
using cached data until manually refreshed.
* When manually refreshed, we initially fetch a few pages instead
of only one. Also, on scroll, we try as best as we can to always keep
10 pages (pages as in screen estate) worth of data loaded.
Better handling of startup (login activity would reset if put in the background).
Allow use of schemeless hostname for login.
Destroy main activity and clear cache on logout.
Change of endpoint for favorites retrieval for one with much better performance.