Add options for automatic work, or automatic break.

This adds two separate options for automatically starting the break timer, or automatically starting the work timer. It's integrated into the option system, and makes sure the notifications don't disappear immediately. Since the settings can be set separately, you don't get stuck like in pull request 36.

Personally I only use the starting the break timer automatically. Still, anyone using both can turn the automatic starting off in the settings when they want to stop.

It should work out of the box, but if you don't want to change anything in the default behavior you should set autostartBreak to false in the defaults.

Cheers,
Marius