Scheduling of breaks - improved approach

[hovancik]

this comment will be updated with the latest thinking

Stretchly should update timers right away, when preferences are updated.

• so that we do not get Mini Break after they are disabled

There should be option to remember current times passed when Stretchly is being paused/dnd/idle/sleep.

• so that after resume we continue with state right before pause (breaks are not reset)