[fix] Solver factory is available from Dune 2.7

See merge request !2003

[test] Remove Python 2/3 compatibility

See merge request !2000

[test] Update shebang to python3

See merge request !1998

[readme] Update test badges

See merge request !1996

Feature/2d segment segment intersections

See merge request !1991

[fluidmatrixinteraction] Use std::clamp for improved readability

See merge request !1992

[examples] Improve 2pinfiltration example documentation

Closes #862 and #854

See merge request !1979

Improve free-flow example

Closes #855

See merge request !1976

Fix/shallowwater example test

See merge request !1986

[common] Fix missing include in parameters

See merge request !1987

[examples][swe][fix] Update reference solution after change of boundary conditions in 8732166a

Fix/shallowwater

See merge request !1984

[linear][istlsolverfactorybackend] Make usable with dune 2.7

See merge request !1982

* throw exception when used in parallel because this feature
is only available for >= 2.7.1

Feature/cleanup fvproblem dependencies

See merge request !1977

Improve shallowwater example

Closes #853

See merge request !1937

[examples] Rebuild after removing deprecated code

See merge request !1978