We need to support models which have multiple phases. This is potentially difficult because the energy of the system would be the disagreement between the experimental PDF and that which is a sum or the model PDFs, not a one to one like our current system
TODO:
[ ] Need to have the various scatter methods support a list of atoms objects, pretty much for loop through all the atoms objects, potentially recursively.
[ ] Need to figure out how to apply a calculator to a list of atoms, may need to make a multi phase model object which is atoms like except that it is a list of atoms
[ ] The forces need to return a list of arrays, one array associated with each phase
We need to support models which have multiple phases. This is potentially difficult because the energy of the system would be the disagreement between the experimental PDF and that which is a sum or the model PDFs, not a one to one like our current system TODO: