WIP commit: started on UI notifications.
At this point, I have basic css/html for a list of elements that slide in from the top of the screen, and a couple of buttons for adding/removing them for testing purposes.
More work on notifications.
Added a deletion+undeletion message, tweaked the internals and usage of the Notification class, and added auto-creation for Notifications based off of `<notification>` elements when the page loads, and `new-notification` events triggered on the `$(document)`.
Added the DeletePending state for TracingTargets.
Now when the user clicks the Delete link for a trace, the TraceManager sets the state of the trace to DeletePending, then waits 15 seconds before actually removing the trace. During that 15 seconds, the user has the opportunity to cancel the pending deletion via a TraceDeleted notification.
Fixed notification dismissal on the backend.
Also fixed the TraceList rendering so that a deletion-pending item slides out when the deletion is scheduled, but doesn't actually get removed until it's gone from the trace list.
Added the LoadingFailed state for TracingTargets.
This helps the UI distinguish between "deleted because of the user" and "deleted because loading failed".
Don't count deleted/deleting traces in naming conflict checks.
Added a little pie chart countdown widget to auto-dismiss notifications.
Removed the "test notification" button
Merge branch 'master' into feature/notification-system

Conflicts:
	codepulse/src/main/scala/com/secdec/codepulse/tracer/TraceAPIServer.scala