Added macro to specify list of coordinate index parameters.
Changed datum_ref function that accepts one argument to operator[] funciton.
Fixed get_site_index function so that it now actually returns an int!
Added definition of operator() functions.
Added docstrings to the operator() functions in LatticeArray
Added operator[] function implementations to LatticeArray
Added more comments to LatticeArray declaration.
Added comment on _block_volume in LatticeArray
Improved comments in operator[] functions.
Added implementation of datum_ref functions.