Adds db install / uninstall

#fixes #50 

Adds `message_broker_producer` database table.

**To test**
- Disable -> uninstall / re-install module.
- Check for `message_broker_producer` table in database.
  - `vagrant@dev:/var/www/vagrant/html$ drush sql-cli`
  - `use dosomething`
  - `show tables`
  - `explain message_broker_producer`
- Disable -> uninstall again to confirm database is removed.

**Note**: Your local vagrant database installation will have to be rebuilt after testing as all of the message_broker_producer variable settings will be removed in the uninstall step.

Related:
#32 
Minor, but common naming conventions in Drupal and in our custom tables would just call this field `updated`.