Allow users to create, save and load presets of intervals

[navinthomas]

This would allow users to create presets and switch easily depending on the kind of work they do. The presets can be like:

• Standard Pomodoro
  Work: 25 mins; Short rest: 5 mins; Long rest: 15 mins; Work intervals in a set: 4
• Longer Pomodoro
  Work: 50 mins; Short rest: 10 mins; Long rest: 30 mins; Work intervals in a set: 3
• 52/17 Productivity Rule
  Work: 52 mins; Short rest: 17 mins; Long rest: N/A; Work intervals in a set: N/A

I think the Standard Pomodoro preset and the 52/17 Productivity Rule preset can be pre-delivered as presets that come along with the app by default. Users can either edit those presets, or create new custom ones like, for example, the longer Pomodoro one.