Mixed periodicity MATLAB interpolators and mimetic C++ interpolators

[bewagner1]

The MATLAB interpolators the higher dimensional counterparts of interpolAToB1D.m and their periodic variants do not allow for mixed periodicity (ie periodic in x but non-periodic in y), while the div, grad, and lap operators do.

Additionally, piggy backing off of #303, none of the interpolAToB1D.m operators are implemented in C++. The interpolators implemented in C++ are the interpol.m and interpolD.m operators, which are only second order.

[Tony-Drummond]

Hi @bewagner1 , Thanks for the issue, @joehellmers has been working on the C++ interpolators. It would be great to coordinate this work.