Rc/toroidal angle

[f0uriest]

• [ ] near axis constraints with omega
• [ ] constant offset surface
• [ ] Proximal projection
• [ ] Add stuff for spectral condensation / optimal fitting
• [ ] Default to fixing zeta==phi?
• [ ] to_FourierRZCurve methods should now be possible?
• [ ] Fix calculation of A, a_major/a_minor, other stuff that needs to be computed at const phi, not const zeta
• [ ] changing continuation/perturbation to work with the new coordinates (changing regularization)

Resolves #465