[parallel][solver] Use passed ParallelTraits instead of local alias

Closes #845

See merge request !1923

[efftoabs][2p] Remove underscore from public member function names

See merge request !1922

Cleanup/wetting-phase-index

Closes #834

See merge request !1918

[mimetic][2p] At default to switch that throws NotImplemented

See merge request !1920

Gets rid of compiler warning about non-treated enum case.

[linear] Fix wrong deprecation message

See merge request !1919

[examples] Implement Python-only doc generator using pyparsing

See merge request !1914

* Adds whitespaces before and after code blocks
* Removes some superfluous white space in code blocks
* Some small changes regarding header guards and formatting

Cleanup/use c++17 is invokable

See merge request !1917

Feature/use more c++17

See merge request !1916

Christoph Grüninger authored 4 years ago and Timo Koch committed 4 years ago

GCC 10 complains about missing size_t

Cleanup/remove outdated deprecations

See merge request !1876

Feature/modify python examples docgen

See merge request !1915