Vectorized tensor utilities

In FEM formulation for mechanics deformation gradient and the like second order tensors are stored as a vector for computational purposes and not as 3x3 matrices. This MR adds identity and determinant computations on these representations and some helper utilities (conversion to 3x3 matrices and back) for testing purposes.

First commit adds the code with tests, while subsequent commits make use of the new code in ProcessLib.

The determinant is not yet used, but will be in upcoming merge request adding so called volume ratio output in LargeDeformation process.

1. Feature description was added to the changelog
2. Tests covering your feature were added?
3. Any new feature or behavior change was documented?