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.