- Controller.Result is now a class rather than an interface,
so subclasses don't have to implement empty methods.
- Replaced Threads with AsyncTasks, which is more light weighted
because it uses pooled threads.
- Removed the Result argument from Controller's methods.
These argumetns weren't used, except in serviceCheckMail.
Regarding serviceCheckMail, the new code behave differenly from the old code.
If there's already listeners registered when it's colled, they wouldn't get
called in the old code, but they will in the new code.
But I think this difference is okay because that's how it works for
POP/IMAP accounts.
Change-Id: I37a857ce7c089c1a411cb7f1fcfcb72c9f5fd2a6
3f545a4060