Implement 2D version of SRHD

See merge request !46

* fix unit tests

* disambiguate timestep overloads

* premature optimization

* fix type instabilities

* implement smooth_diagonal initial data

* quick shot implementation

Implement 2d Euler equations & rework `@with_signature`

See merge request !45

* fix integration tests

* fix unit tests

* make Tree type stable

* rework @with_signature

- allow for multiple @accepts
- add a Prefix(...) option to disambig vars from multiple @accepts
- test with EulerEq2, replacing previous draft

* fix typo in error message

* quick shot on euler 2d

Rework mesh

See merge request !43

* remove RefVector residuals

* make ObjectCache typestable

* fix riemann solver tests

* add burgers2d periodic test

* make 2d equations only return maximum velocity

* adjust broadcasting of boundaryconditions to use new numflux signature

* migrate EulerEq and SRHD

* simplify numerical flux computation, part 3

- migrate 1d mesh versions
- boundary conditions were disabled for now
- added projection method to unitfy numerical flux computations in
  different dims

* fix 2d riemann solver constructors and flux computations

* simplify numerical flux computation, pt 2

- only return one value instead of a tuple from a numerical flux
  function; whatever we did before was unnecessary and probably wrong
- atm this breaks the 1d tests, but will fix this next

* simplify numerical flux computation, pt 1

* cleanup parameter docs and some other comments

* implemente Burgers2d

* fix more unit tests

* fix integration tests

* fix integration tests

* fix unit tests

* also add parfile for 2d advection test

* IntegrationTests: track ref tomls

* hack in support for normal vectors in bdry flux computations

* make cache member of mesh in preparation of eliminating cache from all interfaces

* add integration test for 2d advection

* prepare output reader to deal with 2d outputs and update ref tests

* hack in Mesh2d DG evolution -- needs a bit of refactoring

* fix mesh in save callback

* ScalarEq: make advection_v parameter dimension agnostic

* change mesh parameter xrange to range and update tests

* update Mesh constructors

* add 2d output options

* ScalarEq: fix time step computation to use smallest grid distance; update ref tests

* fix timestep computation scalareq

* make 2d DG work

* scalareq: dispatch timestep also on mesh

* make ScalarEq 1d work again

* fix offsets, iterate and invdetJ in mesh

* xdmf: add cell idx to scalars

* also report error message when running a ref test failed

* catch h5 load errors in IntegrationTests

* add xdmf output utils

* add eachcell method to iterate over the cell data of a bulk array

* add cell data offset to mesh

* extend cache to 2d mesh

* generalize helpfers for mesh

* fix flux for scalareq

* fix periodize

* fix 2

* fix dg_rhs

* add 2d riemann solver

* draft advection 2d

* more exports

* fix dg rhs 3

* fix dg rhs 2

* fix dg rhs

* remove whitespaces

* implement 2d dg rhs

* use vreshape and mul! in dg computation

* add mesh2d constructor

* adjust show method

* fix unit tests

* adjust runtests args

* use tci.method=mda for avtci test

* fix euler sod shock tube test

* fix tests

* remove unused buffer

* rework mesh to organize cells in a tree

* add widths for boxes

* remove unused

* fix box placement

* fix connecting periodic boundaries for tree3d; fix place_boxes algorithm

* fix connecting periodic boundaries for tree2d

* add refvector and tests

* add utility for box

* clean up spectralelement

* remove unused file

* overload sizehint for objectcache

* implement tree structure incl tests

* also include box.jl

* add box

* remove fd.jl

* add tensorbasis

* add numeric utils tests

* cleanup

* separate numeric utilities

* add object cache

Fixallocs

See merge request !42

Migrate cons2prim rework in GRHD project

See merge request !40