Make BlockFragment use database

It works, er, sort of, really slowly and erratically. Rather than fixing
it, next up is a new SyncAdapter!
Cleanup of .news package, @NotNull

Renamed BlockListAdapter > ActvsListAdapter, ScheduleListAdapter >
BlocksListAdapter to reflect what the adapters actually show.
@NotNull and @Nullable annotations! In the news package only for now.
Right now they're hecking annoying but we'll see if that changes.