Fixed bugs with changing max/min of priors within Cosmological and Interped classes

Within the Interped (core) class, it now yields an error if the maximum is increased (or minimum decreased) post-initialization. The attributes min_limit and max_limit keep track of the original boundaries of the provided arrays, such that the maximum can be decreased and then later increased back to the original value without yielding errors.

Within the Cosmological (gw) class, the distance arrays are recalculated when the boundaries are extended, so the maximum can be increased (or minimum decreased) post-initialization.