[aprssig] Throttleing EchoLink Objects

[Jason KG4WSV]

A possible solution, if someone has the server capability to implement
it, would be to set up a parallel -IS for echolink.  Since there are
currently no consumers of the data, traffic would be light.

This could be a data source for individual hams, local igates, or
filtered regional feeds (provided the data doesn't feed back into
APRS-IS, not sure how that one works).

Data from the "echolink-IS" server traffic can tell us about demand,
bandwidth, etc.

-Jason
kg4wsv