preliminary threading infra for local problems
adds thread partition visualization
adds combined output to thread vis.
subgrid_list gets a size method
[thread_vis] adds corase cell visualization
always use Fem::GlobalRefine to ensure DofManager consistency
switch to new dune-stuff function interface
fix massweight parent class
[cmake] remove obsolete config.cmake header
refactor ell. homogenizer
more homogenizer refactor
more signedness warnings fixed
Don't use Fem::BinaryFileIOStream, does not work
hide DiscreteFunction{Reader/Writer} behind DiscreteFunctionIO to prepare move to in-memory backend
rewrites DF-IO to use shred_ptr
[cmake] move hmm code to its lib
removes a stray chdir
fixes lod+fem target compile
[df_io] keep caches of reader/writers
[df_io] keeps functions in memory