[staggered] Add Beavers-Josef-Saffman BC

See merge request !1066

Feature/freeflow misc

See merge request !1065

* fluxes over all faces (except the one on the boundary)
  need to be considerd

* this makes coupling with, e.g., Darcy domains much easiert, as the same fluid system can be used for both domains
* add fluidSystemPhaseIdx to model traits and indices, where necessary
* add some docu

[ransnc][oneeq] Implement a compositional one-equation

See merge request !1059

Freeflow/improve wall functions

See merge request !1062

[sequential] problems can choose the gridView

See merge request !1045

Feature/init twop immiscible

See merge request !1063

Fix/zero initialize all fluidstates

See merge request !1057

Freeflow/oneeq

See merge request !1058

Fix problem with sanitizelinks.sh

Freeflow/improve scvf

See merge request !1056

[rans][twoeq] Implement turbulent dilation term

Closes #514

See merge request !1049

* directioSign() : int
* directionIdx() : unsigned int