Various tweaks to try to improve low memory behavior.

- Reduce the amount that we ask processes to GC after a significant
  operation occurs, but introducing a minimum time between GCs and
  using this in various ways to schedule them.

- Don't spam all of the processes with onLowMemory().  Now deliver
  these using the same gc facility, so we do the processes one at a
  time, and don't allow the same process to get this call more than
  once a minute.

- Increase the time a service must run before we will reset its
  restart delay to 30 minutes (from 10).

- Increase the restart delay multiplication factor from 2 to 4.

- Ensure that we don't restart more than one service every 10 seconds
  (unless some external event causes a service's process to be started
  for some other reason of course).

- Increase the amount of time that a service must run before we
  decide to lower it to a background process.

And some other things:

- Catch IllegalArgumentException in ViewRoot like we do for no
  resources to avoid the system process crashing.

- Fix a number of places where we were missing breaks between the
  activity manager's message dispatch func(!!).

- Fix reason printed for processes in the background.

- Print the list of processing waiting to GC.