Add Tensor Product Operation #109
Description
Add tensor product operation for MeshArrays that supports the following examples:
G(m1, m2, m3, m4, m5) = G1(m1, m2, m3)*G2(m1, m4, m5)
which corresponds to the Einstein summation:
G = einsum('bij,bkl->bijkl', G1, G2)
Here m1...m5 are the meshes. User should be able to specify the dimensions for contraction.