Added model classes and hibernate mappings

- Added classes to represent my own synset and a Supersense
- Added hibernate annotations to model classes relating them and making
the database constraints creation possible.
Implementation of DAO classes

- Added DAO and respective interface to Supersense object;
- Added DAO and respective interface to MySynset object;
- Changes to MITWordnetUtils to use Lexical Files IDs as map index on
listAllSynsets() method;
Fixed SemanticTypes.sql file name