Improvements to TOV evolutions, pt 2 (!113)

* wip: stash some tov examples

* update grhd ref tests to use c2p_freeze_atm_reset = false to restore previous behavior

* init c2p_freeze_atm

* fixup logic of freezing atm

* introduce c2p_freeze_atm flag which allows to define when an atmosphere can propagate

* fix time step computation to use maximum of smoothed_mu

* rescale smoothed viscosity by the extrema of D

* add more example parfiles for tov case

* enable c2p_freeze_atm_reset option

* add cons2prim_rescaled_spherical1d_freeze_flags

* add c2p_freeze_atm_reset option

* document perturbation_rho parameter

* update examples

* experiment with partially frozen c2p flags

* don't bernstein in AV computation

* add c2p with partially frozen reset flags

* use buffers for logarithmic AV indicators

* remove isinvalid

* remove dead code

* avoid splat constructor from CallbackSet

* add punctuation to some parameter doc strings