Fixed: use more a regular psycopg2 connection object

- Queue now works fine with a regular psycopg2 connection object
- Same thing for the setup module
Updated: automatically turn the connection of Queue to autocommit
Updated: turn ConnAdapter to a real adapter

- Queue and ConnAdapter objects use a regular psycopg2 connection object
  and set this connection automatically in autocommit mode
- ConnAdapter object is now a real adapter: no inheritance at all
- Worker use a regular connection that is turned into a ConnAdapter for
  internal use but use the same connection to initialize the internal
  queues
- tests have been "adapted"

Note: this is not exactly the same than queue_classic since QC use the
adapter for the Queue object (which is not actually needed).