Add etn_receiver_events layer to OTN Geoserver

[diniangela]

An action item from the ETN-OTN Working group:

Create a new layer (etn_receiver_events) that contains the events in OTN that should be visible to ETN.

• [x] Add the layer to the OTN Geoserver
• [x] Add its column definitions to the layer definitions in the code