Adding the init function. Will need to be updated if more than 3 dimensions are
used, but there is an assert to check this for now.
add face field (not tested)
New Kroneckor products: AXIXI, IXAXI, IXIXA (not thoroughly tested)
Some white space and comment fixes
Bug fix in kroneckor product
Jacobians implemented. Still need to test and store these values. Still need
to compute the normals and surface Jacobians.

Jacobians, normals, and surface Jacobians are only computed when num_Vi == DIM.
If not then Jrx is really xr and not Jrx.