Lego_auto_sc [id two atoms] or [mol res1 res2]
Move along the chain and automatically build side chain by choosing the most frequent rotamer from the database. This requires the coordinates for `N', `CA', `C' atoms for each residue. Useful for putting on starting side chains that may then be checked individually or with RSR commands. Because Ala and Gly residues have no rotamers, they will cause a warning that can be ignored.