feature: improve registry error handling
feature: improve registry error handling

http://registry.npmjs.org/ is returning now {"error":"Service Unavailable"}
and we erroring when we expect `results` or `objects`
to be always present in the response.

SignalK/signalk-server-node,SignalK/signalk-server-node,SignalK/signalk-server-node,SignalK/signalk-server-node