Unify setTimeout scheduling in update function.
Fix CS: quotes
Minor changes.

* Pre-calculate WaTime.next
* Remove separate ui.init, expose ui.update, and call it explicitly
  when interface should be updated (after saving options).
* Use console methods appropriately for warnings/errors/etc.
Fix update scheduling.

* Guard against early updates that might have been resulting in two
  updates in a short period of time.  Reschedule if next update will
  happen in less than a second.
* Remove +100 microsecond hack that was supposed to guarantee it.
* Distinguish scheduled and forced updates: forced always update the
  interface immediately and never ring the bell.