Remote Services Priorities

[debbabi]

Remote Services should have lower priority than local ones.
Also, Remote Services from the same node should have higher priority than those from other nodes.
This can be done by modifying the service ranking property.
local service = no modification
remote service from the same node => -5 (relative to existing service ranking)
remote service from other node => -10 (relative to existing service ranking)

We could apply the same logic for Herald Routing (when be available).