Index class now supports named indexes.
Added support for named indexes to the MysqlAdapter.
Added support to MysqlAdapter for removing indexes by name.
Added support to SQLiteAdapter for naming indexes and removing indexes by name.
Added support to PostgresAdapter for naming indexes and removing indexes by name.
Added unit tests to the Postgres and SQLite adapters for creating tables with named indexes.
Add tests for DropIndex() with name specified.
Fix PostgresAdapter so DropIndex() works if a name was specified when the index was created.
Merge pull request #196 from archer308/namedindexes

Add support for naming indexes