0.7.2

To remove unnecessary Kuzzle dependencies from the router controller and to prepare the incoming protocol plugins, this pull request changes the way the router controller handles worker responses, following @stafyniaksacha suggestion:

• renamed core/responseListener to core/workerListener to make it easier to understand what it does
• removed all references to the workerListener from the router controller. Also removed empty promises handling. Promises resulting from calls to the funnel controller now always resolve to the according responseObject
• the main Kuzzle object now contains a global workerListener instance
• controllers behind the funnel controller now always return a promise resolving to the awaited response, either directly, or by returning the result of workerListener.add
• the workerListener now awaits worker responses using the internal broker, and resolve/reject the stored promises, letting the router controller respond to the requesting client. It doesn't notify directly anymore.