Andronome updates
- Menu buttons for enabling/disabling sound and blink.
- Made sure tempo setting is stored between invocations.
- Form-and-fit for larger screens improved.
- Usage screen only shown once (at first start-up) and on request.
- Reduced memory allocations (less footprint and better performance).
- Some internal restructuring to allow for future enhancements (looking forward to version 1.0.0...).