Modified to use an initial e2d value for the first plasticity calculation and output the dilatation rate

Modified nonlinear iteration convergence criterion to calculate the maximum velocity difference between iterations over the maximum vector length from the previous iteration

Added input of matrule to determine whether divFEM, majority or minority volume is used for material assignment in elements. Added input of bulkvisc to determine whether a penalty value or bulk viscosity is input. Added input of init_e2d to specify whether or not plastic materials should have their effective viscosity calculated using an initial strain rate.

Added option to assign material properties using a majority or minority rule, to complement what is done with DivFEM