easier_terms: manage mappings in Field
easier_terms: manage mappings in Field

- new Field.clear_mappings(), .save_mappings(), .create_mapping(),
  .get_mapping()

rc/sfepy,vlukes/sfepy,sfepy/sfepy,vlukes/sfepy,BubuLK/sfepy,rc/sfepy,RexFuzzle/sfepy,lokik/sfepy,rc/sfepy,sfepy/sfepy,vlukes/sfepy,RexFuzzle/sfepy,lokik/sfepy,RexFuzzle/sfepy,BubuLK/sfepy,BubuLK/sfepy,lokik/sfepy,lokik/sfepy,RexFuzzle/sfepy,sfepy/sfepy