[io][imagereader] Fix compiler warning about unnecessary references. Image values are simple types use value type.

[changelog] Add remark on pip installation

See merge request !2451

[python] Make DuMux installable via pip

See merge request !2419

Feature/remove test implicit layer

Closes #982

See merge request !2447

Feature/separate sequential tests

See merge request !2445

Cleanup/some cmakelists

See merge request !2446

[test] Test requires UMFPack

See merge request !2442

Feature/fix assembler parallel warning

See merge request !2439

Fix/fvassembler include

See merge request !2424

Dennis Gläser authored 4 years ago and Timo Koch committed 4 years ago

On minimal setups without MPI installed, the box tests failed to compile
as the FVAssembler uses the ParallelVectorHelper class, which itself was
hidden behind a HAVE_MPI guard. Tests with setups where MPI is not
installed showed that the tests compile and run also without the guard.

[test][richards] Add two benchmark cases Vanderborght 2005

See merge request !2432

Fix/material spline capture

See merge request !2440