Tracker view: Add realtime updates

[cdhowie]

Have the frontend maintain a WebSocket connection to the server through which changes made by other users can be pushed. This will largely replace the “refresh” button, except the button can still be used to request that the backend pull an update from the AP server.

[cdhowie]

There is a potential issue with this feature that occurred to me last night. If someone makes a change (or requests an update from AP) that causes the sorted order of slots to change, this could make it very easy to accidentally make a change to a different slot than one was originally intending. This problem needs to be solved before I will feel comfortable implementing this feature.