Add debug check on deformation rate tensor

One of our users was recently trying to run the python code and was trying to do something like:

# Pure deviatoric case so no pressure produced
d_svec_kk_sm[0] = 0.5*erate
d_svec_kk_sm[1] = 0.5*erate
d_svec_kk_sm[2] = -1.0*erate
# expected this case to result in pressure
d_svec_kk_sm[0] = 0.0*erate
d_svec_kk_sm[1] = 0.0*erate
d_svec_kk_sm[2] = -1.0*erate

This made me realize that I should just provide a convenient wrapper for users that take in a velocity gradient (or gradients) that then produces the necessary deformation rate and spin tensors that ECMech uses. Next, it also made we realize that we have no check within the code to ensure the deformation tensor in our format is actually a deviatoric tensor + volume term. We should add a check at least in debug mode to at least ensure this is the case.