Various for 2.0a9

[bpuchala]

Fixed

• Fix CASM::xtal::make_primitive, which was not copying unique_names. This also fixes the output of libcasm.xtal.make_primitive which was losing the occ_dof list as a result.
• Fix JSON output of xtal::BasicStructure site label

Changed

• Changed make_primitive to act on either Prim or Structure.
• Changed default of xtal.Structure.to_dict to output in fractional coordinates
• Added excluded_species and frac parameters to xtal.Structure.to_dict

Added

• Add to libcasm.xtal: make_primitive_prim (equivalent to current make_primitive), make_primitive_structure, and make_canonical_structure.
• Add options to the BCC and FCC structure factory functions in libcasm.xtal.structures to make the conventional cubic unit cells.
• Add to libcasm.xtal: StructureAtomInfo namedtuple, and methods sort_structure_by_atom_info, sort_structure_by_atom_type, sort_structure_by_atom_coordinate_frac, and sort_structure_by_atom_coordinate_cart
• Add to libcasm.xtal: substitute_structure_species
• Add to libcasm.xtal.Prim: method labels, constructor parameter labels
• Add to libcasm.xtal.Lattice: methods reciprocal, volume, lengths_and_angles, from_lengths_and_angles
• Added unit_cell, diagonal_only, and fixed_shape parameters to libcasm.xtal.enumerate_superlattices.