Fixes COMETD-455 (Allow to configure ws.maxMessageSize in OortComet).

Now OortComets will use the value configured for the Oort that owns
them.
Fixes COMETD-456 (Seti does not update presences on remote node crash).

Now Seti updates the presence on the comet left event.
[maven-release-plugin] prepare release 2.7.0-beta2
[maven-release-plugin] prepare for next development iteration
Merged branch '2.7.x' into 'master'.