Add New Database now opens in tray, not prompt

This PR changes the Add New Database from a prompt() to a tray. 

@seanbarclay, if you have time, would you mind taking a glance at this? I'll post a screenshot of the before + after in the jira ticket:
https://issues.apache.org/jira/browse/COUCHDB-2398

** this isn't ready to merge yet. I'd the appearance of the tray to be reviewed. **