Bring new sbt services using the event stream api

removes the old sbt.js apis. Now, you have to use the new Websocket and EventStram API

```js
define(['commons/websocket', 'commons/types'], function(websocket, types){

  var stdout = ko.observableArray([]);
  websocket
    .subscribe({ type: 'sbt', subType: 'LogEvent', event: { entry: { message: String, type: "stdout" } } })
    .each(function(message){
      stdout.push(message);
    });

})
```


When we `fork` the eventstream {A}, it's not as in Scala: we do not recover a new copy {A'} of the stream {A}, but we just create an empty stream {B} where every event from {A} are pushed to {B}. That way, we are keeping references and we do not execute the same code multiple times if we don't need it.

Also... Thanks to `EventStreamExecution`, this whole thing is very Fast at execution. all the cost is on startup. I haven't benchmarked the Type checking though. but it's really just a couple of ifs, so if we keep the Patterns simple we should be fine.