Correct handling of Directive controllers

[jokade]

Controllers for Directives must be handled differently than normal controllers:
for a controller defined on a directive angular creates a empty object which is then passed as thisto the controller constructor; every directive defined on a tag then may add members to the passed in this.
The current (0.1) implementation does not handle this correctly (see discussion on on issue #28).

[jokade]

Solution: use controller function and define controller as a facade trait instead of a Scala class;

Remodelled Directive API:

trait MyDirectiveCtrl extends js.Object {
  var click() : js.Function = js.native
}

class MyDirective {
  override type ControllerType = MyDirectiveCtrl
  override type ScopeType = js.Dynamic
  override val controllerAs = "ctrl"

  override val isolateScope = js.Dictionary(
    "foo" -> "=bar"
  }

  override def controller(ctrl: ControllerType, scope: ScopeType, elem: JQLite, attrs: Attributes) : Unit = {
    ctrl.click() = () => {
      /* ... */
    }
  }

  override def postLink(scope: ScopeType, element: JQLite, attrs: Attributes, ctrl: ControllerType): Unit = {
     /* ... */
  } 
}