GeoOverlay Area Entities

[salsajeries]

• Each Circle/Polygon GeoOverlay should be able to list all entities (visualizations, fois(?), other GeoOverlays(?)) with location in its area, regardless of geofence inclusion/exclusion.
• These lists should be live tracking updates to locations, i.e. listening to active websockets when applicable

[salsajeries]

BLOCKED: Implementation details need to be confirmed regarding datasource listening. Might be related to #181 if looking to use a store for all active datasources project-wide