Refactor MaterialTensorAux ref #2725

Create new MaterialTensorCalculator class that provides a
common interface to methods to calculate scalar quantities
from material tensors.  Also add ability to calculate
directions from those quantities where applicable.
Merge pull request #2733 from bwspenc/material_tensor_2725

Refactor MaterialTensorAux ref #2725
Merge commit '54c7e109b87b460ab2a0b14d254a34e0fd110430'