* restricting the use of this fluidstate for numPhases == numComponent
  is actually not necessary

* components other than the main component are always zero anyway

* removing this assert does not break anything but allows using the OnePAdapterFluidsystem
  in combination with immiscible fluidsystems

[fluidsystems] Add a 1p adapter fluidsystem for multi-phase fluid systems

Closes #528

See merge request !1112

We can use one-phase adapter for reusing m-phase fluid systems now.
Reverts 7bb9a857 which introduced a bug for the diffusion coefficients

[material] introduce brine fluid system and test

See merge request !1033

This makes use of the introduced fluid state adapter for mapping to the right
phase and component indices.

This fixes:
- calculation of the liquid mixture density (for the case of it being composition-depent)
- make fugacity coefficient of NaCl zero (we assume NaCl to stay in the
water phase anyway throughout this fluid system)
- adapt reference solution

Fix/h2oheavyoil

See merge request !1111

Freeflow/fix eddy thermal conductivity

See merge request !1110

previous implementation could potentially result in unwanted forward calls in the fluid system

[cmake] Fix guards for foamgrid

See merge request !1109

Rename output field temperature -> T for consistency with p and S

See merge request !1106