Added CartesianGrid::inputCellCollectionOfScalar

- Added CartesianGrid::param_ member.
Added CartesianGrid::inputCellCollectionOfScalar
Merge branch 'cartesian' of https://github.com/sintefmath/equelle into cartesian
Doxygen documentation fixes.
Merge branch 'cartesian' of https://github.com/sintefmath/equelle into cartesian
Try to speed up linking time of CartesianGrid
Documentation update.
Ensure consistent ordering of face properties.
Documentation updates.

- Removed CartesianGrid::getStrides as it served no purpose.
- Better error checking.
Disable output for ParameterGroups created in tests.
Introduced cellOrigin member variable, this speeds up cellAt a lot.
Converted faceStrides and and number_of_faces_with_ghost_cells int
std::arrays.

- This mandatates that Dimension must be an enum and not a class enum.
Made const versions of CartesianGrid::cellAt and CartesianGrid::faceAt