Add filtering to the Dashboard

We have users that are based in specific locations and when they are logged in to Administrate and are taken to the dashboard (.../ux/dashboard) they are presented with conflicts of all locations.

Ideally we would like the ability to filter the dashboard so that the conflicts that are for events in a specific location are displayed to the user.

This means that the user can quickly identify conflicts that are related to their location so that they can resolve the ones relevant to them.