Class ExpandAsymmetricUnit

Expand asymmetric unit and anisotropic thermal displacement

Data members:
    spacegroup  -- instance of SpaceGroup
    corepos     -- list of positions in asymmetric unit,
                   it may contain duplicates
    coreUijs    -- thermal factors for corepos (defaults to zeros)
    sgoffset    -- optional offset of space group origin [0, 0, 0]
    eps         -- cutoff for equivalent positions
Calculated data members:
    multiplicity -- multiplicity of each site in corepos
    Uisotropy   -- bool flags for isotropic sites in corepos
    expandedpos -- list of equivalent positions per each site in corepos
    expandedUijs -- list of thermal factors per each site in corepos

Initialize and calculate instance of ExpandAsymmetricUnit

spacegroup   -- instance of SpaceGroup
corepos      -- list of positions in asymmetric unit,
                it may contain duplicates
coreUijs     -- thermal factors for corepos (defaults to zeros)
sgoffset     -- offset of space group origin [0, 0, 0]
eps          -- cutoff for duplicate positions