added the xstr method; fixed bug with string comparison in the idx method; implemented parallel option in the split method; added labels and units to the coefficient objects; revised the join method, removing some bugs; added the default and str methods; fixed a minor issue in the assemble method; implemented the table method
added the xstr method; fixed bug with string comparison in the idx method; implemented parallel option in the split method; added labels and units to the coefficient objects; revised the join method, removing some bugs; added the default and str methods; fixed a minor issue in the assemble method; implemented the table method

jgte/orb,jgte/orb,jgte/orb,jgte/orb,jgte/orb