Rework notifications

* Improve content of notifications
  * More descriptive title
  * The bug that caused the need for manually assembling the message has been fixed (#161 or c5e548c8ab41435dd22e7d56089fcec767bdf945)
* Permission for displaying notifications can only be requested upon user interaction in Chrome, not on page load. Bind to connect button
* Take user to g-b tab and buffer causing the notification on click
Fix the confirmation dialog when closing the tab

* Only nag if we're connected
* Set event return value so Chrome shows the dialog
Merge pull request #165 from lorenzhs/fixnag

Fix the confirmation dialog when closing the tab
Merge pull request #164 from lorenzhs/notifications

Rework notifications
Set container to panel