Initial spray layer that uses swagger

Currently using swagger-spray which uses annotations to generate swagger doc. Any code generator will need to create these annotated classes like AppMasterService based on an input grammar (which could be swagger like). This class is a simple example of beginning to retrieve AppMaster information from the Master actor. 
I feel this should not be a port of Local. 

Maybe we should move it to a standalone command. Like Rest.scala. And then we can create a sbt shell command like rest.sh.

Usage like this:
rest.sh -master  "host1:port1,host2:port2,host3,port3"

We can get a master ref like ClientContext.scala
```
class ClientContext(masters: Iterable[HostPort]) {

  private implicit val timeout = Timeout(5, TimeUnit.SECONDS)
  val system = ActorSystem("client", Configs.SYSTEM_DEFAULT_CONFIG)

  val master = system.actorOf(Props(classOf[MasterProxy], masters), MASTER)
```