Fixed dual printing of postprocessor table (closes #2686)
Merge pull request #2734 from aeslaughter/pp-2686

Fixed dual printing of postprocessor table
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