adopting mask_phases from lc_geometry results in confusing/ambiguous behavior

[kecnry]

to avoid confusion when adopting the proposed t0 and mask_phases which can then result in a confusing phase-shift.

@kmhambleton

[kecnry]

the mask_phases are currently automatically shifted if adopting mask_phases and t0_supconj at the same time (by passing adopt_parameters=['*'], for example. This should be more clearly documented in the tutorials.

However, if adopting t0_supconj first, and then adopting both mask_phases and t0_supconj, the shift will be based on the current face-value of t0_supconj. This could be "fixed" by storing the original value when running the estimator in the solution so that the shift could be correctly applied at any point later.

Also might be useful to have a function in phoebe.helpers to arbitrarily shift the proposed mask phases (or eclipse edges) by a change in t0 from the t0 used to estimate those mask_phases, etc.