refactor: rename annotations to metadata

BREAKING CHANGE (maybe)

Well as long as our customers use public API this should not be a
breaking change, but we have changed import structure as well as
internal names, so it could be breaking.

import:
  angular2/annotations => angular2/metadata

Classes:
  *Annotations => *Metadata
  renderer.DirectiveMetadata => renderer.RendererDirectiveMetadata
  renderer.ElementBinder => renderer.RendererElementBinder
  impl.Directive => impl.DirectiveMetadata
  impl.Component => impl.ComponentMetadata
  impl.View => impl.ViewMetadata

Closes #3660

modules/angular2/render.ts

@@ -5,7 +5,7 @@
  */
 
 export {
-  DirectiveMetadata,
+  RenderDirectiveMetadata,
   DomRenderer,
   RenderEventDispatcher,
   Renderer,