feat(numtools): sym<->full input check, `...` ability

[jrwrigh]

symmetric2FullTensor and full2SymmetricTensor were changed by:

• Adding a input check to verify that the incoming array was of size (...,6) or (...3,3), respectively
• Add ability for the input array to have arbitrary leading dimensionality.
  • So an array of shape (10,100,6) could be input and transformed to (10,100,3,3)
• Added tests to verify all the above changes.