Rotation scan parameters are misleading

Our parameter model for the rotation scan contains inputs for `scan_width_deg`, `num_images` and `rotation_increment_deg`. These three variables are dependent on each other, and we should only be specifying 2 of them, and the third one should be calculated from this.

The relationship between these variables is `scan_width_deg = num_images * rotation_increment_deg`

I believe this currently results in a bug - the `scan_width_deg` from the parameter model is overridden during `calculate_motion_profile`. We haven't noticed it yet since Hyperion always does 360 degrees

## Acceptance Criteria
- Add a validator in the rotation scan parameter model which checks that at least 2 of the 3 of the above parameters have been filled out. If 2 have been specified, calcualte the third in the validator. If 3 have been specified, make sure they are consistent with each other.