Refactor GRHD project (!101)

* update examples once more

* remove comments

* cleanup: remove codegen for now

* IntegartionTests: add grhd_tov_spherical1d ref test

* IntegrationTests: remove reltol from grhd_bondi_accretion test

* spherical1d: fix missing shift from maxspeed computation

* cleanup

* make spherical1d formulation work when r=0 is included by removing potential nans in source terms by enforcing symmetry

* make impose_symmetry! dispatch on project

* add tov example that runs with spherical1d formulation

* wip: change maxspeed implementation for tov star initial data

* cons2prim: use non-zero values for rho, eps thresholds

* fix: set atm density in bondi_accretion initial data

* implement tov initial data for spherical1d formulation

* add formulation parameter

* implement rhs for FVElement and rescaled_spherical1d

* implement equations for FVElement and rescaled_spherical1d

* mesh: implement differentiate for FVElement

* add grhd example par files

* update notebooks

* fix missing lapse factor in source terms

* fix typos

* fixup initialdata setup

* derivative computation needs jacobi

* rename cons2prim routines

* add atmosphering to cons2prim

* implement rhs! for rescaled_spherical1d formulation

* specialize timespeed computation based on equations

* add specialized equations for the rescaled GRHD version

* implement initialdata setup for tov case

* spherical accretion:make sure K, Gamma agree with loaded data

* expose spectral differentiation

* wrap SphericalAccretion solver into module; recompute bondi_accretion.h5 with less radial points

* refactor TOV solver to use OrdinaryDiffEq

* initialdata: cleanup dir

* add bondi accretion as ref test

* fix up loading of id file

* fv_rhs: implement fv_update_step! with source term

* add ROOTDIR const global so that parfiles can specify paths relative to project root

* update SphericalAccretion.jl

* update sympy nb

* cleanup initialdata setup

* equations: fix up Tmunu computation

* Revert "fix source term in dg and fv rhs computation"

This reverts commit 161cc034.

* Replace Interpolations.jl with BasicInterpolators.jl

* equation: add missing flux terms to sources; use outflow bdry condition on inner radius

* comments in cons2prim

* implement momentum constraint for debugging

* test SphericalAccretion

- copy Bugner's C version of the solver
- compare my results with Bugner's -- good agreement
- compare against literature results (Papadopoulos 1998,1999) --
  discrepancy in sign of vr, ur, otherwise good agreement

* SphericalAccretion: fix wrong definition of uc^r and Vc

* tweak impl more

* fix source term in dg and fv rhs computation

* fix equations and implement fv method

* equations: combine flux and source computation

* math: update spherical_accretion notebook

* SRHD: export module

* re-implemented GRHD eqs with a non-zero shift

* initialdata: add grhd_source.codegen.jl that was generated with TensorComponents.jl

* deps: need Interpolations.jl for initial data setup

* update math/spherical_accretion.py

* update setup

* start initialdata setup for bondi problem

* rework rhs.jl

* update deps and parameters

* update type defs

* initialdata: add HDF5 dep; write h5 output for SphericalAccretion.jl

* rename cons2prim.jl

* remove unused files