JS notification manager

[nickvergessen]

We need something like the php notification manager in JS.
The problem is that when you accept a share via the notifications,
the share popup on the file list should be closed and the file list updated.

Also when accepting the the share in the popup the notification should be removed (not only after the next polling).

[PVince81]

and also what happens if the notification app is disabled, should it fallback to the popup ? (additional code paths to be maintained and tested)