Discovery API: Service interface inherits DOM4 EventTarget.
Aligning with W3C style and makes it possible to use standard addEventListener/removeEventListener methods for APIs that use event handling and inherits the Service interface. Jira issue: http://jira.webinos.org/browse/API-39
Merge pull request #34 from ClaesNilsson/master

Discovery API: Service interface inherits DOM4 EventTarget.