The `3pwateroil` model still uses the method `matrixHeatFlux` from the spatial parameters. This should be made consistent with the other nonisothermal models, namely, by calculating the matrix heat flux in the flux variables using an effective thermal conductivity relation. For the same reasoning, one should rename `heatCapacity` to `solidHeatCapacity`. The test of the `2pnc` model also still provides a function `matrixHeatFlux` in its spatial parameters. This should be removed.