[porousmediumFlow] Export indices in all volVars

See merge request !2229

[docu][freeflow] Improve rans oneeq docu.

See merge request !2251

[material][2p] Move thermalconductivity laws to their own folder

See merge request !2249

[md][embedded] Fix CMakeLists.txt

See merge request !2247

[common] Add inverse of monotone cubic spline

See merge request !2250

* Add missing header

[basegridgeometry] Use more robust way to choose ctor of mappers

Closes #932

See merge request !2245

* use std::is_constructible

[readme] Update link to class documentation

See merge request !2242

[common] make sure dt != 0 in timeloop

Closes #928

See merge request !2237

- don't insert checkpoints at current time
- warn when dt set to 0 and not finished

[cleanup][test] Rename test_md_embedded{dims} to test_md_embedded_{dims}

See merge request !2241

Fix/cc internal dirichlet

Closes #929

See merge request !2240

[bugfix] Fix compiler error introduced in !2236

See merge request !2238

Fix/navier stokes rot sym

Closes #927

See merge request !2236

[common] fix segment index issue in spline extrapolation

Closes #925

See merge request !2235

Resolve "doc shallow water flux"

Closes #924

See merge request !2234

Added some hints to explain that the shallow water Riemann problem works in
2D only. The exact Riemann solver is 1D only and the problem is rotated.
The scvf.area() is given in m.

Add the units of the water flux and momentum fluxes in the documentation.

Add a new opts file that can be used for Docker builds

Closes #919

See merge request !2232