Mad coll

Work done to implement "UW Universal Workflow" functionality.
I think we need add a second argument to the fluka function, 'fractype', just like the MCNP version, which should default to massfractions when unspecified and if specified switches to atom fractions. As it stands now, irrespective we print the fluka compound card as if it atom fractions, i.e.

    COMPOUND        0.04     235-U      0.96     238-U                    URANIUM

However, when we create a Material object in pyne, if no arguments are specified the component nuclides are mass fractions, which should more correctly be 

    COMPOUND       -0.04     235-U     -0.96     238-U                    URANIUM

So in summary, an additional string argument to Material::fluka, which propagates to Material::fluka_compound_str, so when fractype = "mass", the nuclide fractions are -ve and when fractype = "atom", they are positive, however when no arguments are specificied it should default to fractype = 'mass'.

If this is unclear, please let me know