Fix and consolidate model geometries

[keileg]

[mikeljordan]

Tentative Task List:

• Modify parent class "CubeDomainOrthorgonalFracture" to include the method "mesh_argument" and get rid of the derived class "OrthogonalFractures3d"
• Update tests by replacing "OrthogonalFractures3d" with the parent class.
• Update the "RectangularDomainThreeFractures/ geometry" class to use key "grid_type" in params to determine the grid type.
• Update tests accordingly. This may require some attention to ensure that the character of the tests is unchanged.

Fixes to these issues are pushed to this branch Here

[keileg]

Resolved by #1593