Added simple function to calculate linear interpolation of points
Implemented class to handle lattice anisotropy book keeping and initialisation and new parameter to material input file to read in file of tabulated values.
Implemented died and energy calculation of tabulated lattice anisotropy
Added simple utility to calculate lattice anisotropy variation
Bugfix: Corrected sign error in lattice anisotropy field calculation
Removed superfluous lattice anisotropy variables from material class and i/o options