Unsubscribe count field

[jirenius]

Issue

When a client unsubscribes to a resource, the unsubscribe request should have an option count field that states the number of unsubscribes to perform, instead of sending multiple successive unsubscribe requests.

Multiple subscriptions may build up if a call request returns a resource reference for a resource already subscribed.

Notes

• Requires a PATCH version update to the RES Protocol
• Only affects RES Client protocol. Service are unaffected.
• Clients should fall back to legacy behavior if the gateway responds with 1.2.0 or less to the version request,

[jirenius]

Resolved in #162