signal pz sender than receiver disconnected

send a message to the original sender in case the original receiver disappeared.
upon receiving such a message all registered RPC services are notified of the
sessionId that disconnected. this allows the services to stop trying to send
messages to this sessionId.

Jira-issue: WP-851
implement disconnect event for geolocation api

for geoip module, clear timer for sending position updates to a disconnected
session id.

Jira-issue: WP-851