XD-910 Add a processor for restful webservices

Offers the functionality to make http request to a web service. i.e. outbound http gateway.

Example implementations:
stream create --name foo --definition "trigger |rest --reply-timeout=1 --url=http://earthquake.usgs.gov/earthquakes/feed/geojson/all/day|log" | log

stream create --name foos --definition "trigger --payload=lat=34.0567006&lon=-84.34368810000001&site=all&smap=1&searchresult=Roswell%2C%20GA%2030076%2C%20USA#.UktzaWSG1Dd | rest --url=http://forecast.weather.gov/MapClick.php? |log"