Orthotropic elasticity

Use local coordinate system for the coordinate transformations. If no coordinate system is provided, the usual cartesian coordinate system is assumed.

Only 3D case is implemented and rudimentary tested in this PR. Another unfortunate thing is that the local coordinate system must be passed through the process' interfaces to the solid material creation. This can be resolved by creating the materials independent of the process; definitely not this PR.

Commit-wise review is easier, I think.

Changelog updated.