Check if current keep-alive mechanism employed by Restcomm Connect is enough to keep NAT holes open

[atsakiridis]

If it does we can change the REGISTER behaviour to happen every 3600 secs and avoid loading Restcomm Connect without reason

If that doesn't work out we could support RFC5626 in the client for TCP/TLS since it is already supported in Sip Servlets. Specially for UDP where RFC mandates STUN where it's going to be a big change, we could fallback to either REGISTER every minute or use OPTIONS.