Fixed default arguments to class constructor

def __init__(a=[]) does not create a new [] for every class initiation.
Instead check for a==None and create a new one in the method.
Added file with class for cryst plast materials
Added file to facilitate uniaxial test for Abaqus.
Added file to test uniaxial test generator.
Facilitated use of cobolt and WC

Added method to read volumes from stat file from Neper.

Added method to assign Cobolt and WC to polyhedras.

Made it so that if Cobolt and WC is assigned then createCohesiveElements
only creates elements between C/WC and WC/WC.
Updated for WC Cobolt