make shock tube and blast wave tests run for SRHD when using MDA AV (!91)

* update ref test data srhd_simple_wave_avmda

* fix up dispatch of register_variables; fix up smoothing on initial data

* mda: use inplace operations

* cons2prim: disable simd; disable atmosphering warning

* update blastwave1/2 av mda examples

* adjust tau when energy density exceeds lower bound

* don't recompute max speed for timestep

* determine initial viscosity using all dynamic variables as indicators

* add blastwave1 example

* add blastwave2 examples

* fixup blastwave2 test; don't smooth FVElement mesh initial data

* commit conservative_fixing experiments (not active)

* cons2prim: temporarily error in case speed is too large

* disable conservative_fixing again

* change fixedprms in setup

* fix domain assertion for blastwave1 test

* add initial data smoother based on Bernsteining

* do not recompute viscosity on initial data

* modify examples

* implement fd derivative again

* implement covariant regularization

* add prms to Project type

* add example parfiles

* update ref test data srhd_simple_wave_fv

the difference is quite pronounced

* use maximum of max_v instead of v for time step estimation

* update ref test data srhd_simple_wave_avmda

* compute cellmax_v properly; compute maxspeed in equation callback

* implement sod shock tube initial data