feat(Directive): Have a single Directive.host which mimics HTML

fixes #2268

BREAKING CHANGE:

Before

    @Directive({
      hostListeners: {'event': 'statement'},
      hostProperties: {'expression': 'hostProp'},
      hostAttributes: {'attr': 'value'},
      hostActions: {'action': 'statement'}
    })

After

    @Directive({
      host: {
        '(event)': 'statement',
        '[hostProp]': 'expression'  // k & v swapped
        'attr': 'value',
        '@action': 'statement'
      }
    })

modules/angular2_material/src/components/button/button.ts

@@ -12,8 +12,7 @@ export class MdButton {
 @Component({
   selector: '[md-button][href]',
   properties: ['disabled'],
-  hostListeners: {'click': 'onClick($event)'},
-  hostProperties: {'tabIndex': 'tabIndex'},
+  host: {'(click)': 'onClick($event)', '[tabIndex]': 'tabIndex'},
   lifecycle: [onChange]
 })
 @View({templateUrl: 'angular2_material/src/components/button/button.html'})