Move one-to-three protein letter maps into Bio.Data.IUPACData
SeqUtils.seq3 now creates a copy of the imported IUPACData dict

This is to prevent a bug where the IUPACData dict is imported in some other
modules, and the key-value pairs have unexpected values due to seq3's update.
Move Bio.SCOP.three_to_one_dict to Bio.Data.SCOPData
Add deprecation warning in place of old SCOP's 3-to-1 dict
IUPACData: fixed small typo protein_letters_31to1 -> protein_letters_3to1