Power calibrations: spindown checks with resistance

[drmason789]

Extending #81

For a selection of resistance levels L

• the user spins the flywheel up to 900 RPM then lets it spin freely
• the app applies resistance L
• the app measures the deceleration down to 0RPM

Determine how interpolateable the results are. It would be more convenient to be able to get an accurate result from 50, 100, 150, 200, 250 than having to do it at every 10th increment, for example.

This could vary from bike to bike because it will depend on the condition of the solenoid and how close it is fixed to the wheel. This is adjustable.