Pre-break notification and postponeable breaks

The main new feature of this release is pre-break notifications:

• It's a non-blocking "bubble" which comes up at a preset time before the break would occur.
• It's amount can be set in settings
• Two modes available: permissive and restrictive

When the notification "bubble" comes up it informs the user which kind of break is coming, and there is a choice:

• You can either ignore, click on the break button, or postpone

This is where the two modes come up:

• Restrictive mode (default):
  • If you do not want a break then you have to click on the button. Not clicking brings up the break when the time is up.
• Permissive mode:
  • You only have to click if you want to have a break! Not clicking will result in nothing happening. Timers get reset, the whole cycle restarts like you had a break.

You also have to option to postpone the break. The length is set by the user in settings, also the amount.

So if you have '2x' for amount and '2 min' for time, then clicking on the 'postpone' button will make the notification go away, and it will only come again after two minutes. You can postpone like this for one more time, when you will either have a break or not. It will not be allowed to postpone again.

I hope these will make this little app even more useful! As always, suggetions are very much welcome!

See the rest of the things in the changelog!