This PR
- Move the logic related to this optic into specific methods
- Implement the inherited
move_magnification - Update exposed target magnification
- Update the final magnification (after a move) from motor locations
- Added unittest (using config from BM18)
The tests show that there is a huge discrepancy between requested magnification, and resulting magnification (requested mag -> move motor -> motor pos -> computed mag). I can't tell if it is normal or not.