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/test/render/api_spec.ts

@@ -1,4 +1,4 @@
-import {DirectiveMetadata} from 'angular2/src/render/api';
+import {RenderDirectiveMetadata} from 'angular2/src/render/api';
 
 import {MapWrapper} from 'angular2/src/facade/collection';
 import {ddescribe, describe, expect, it} from 'angular2/test_lib';
@@ -7,7 +7,7 @@ export function main() {
   describe('Metadata', () => {
     describe('host', () => {
       it('should parse host configuration', () => {
-        var md = DirectiveMetadata.create({
+        var md = RenderDirectiveMetadata.create({
           host: MapWrapper.createFromPairs([
             ['(event)', 'eventVal'],
             ['[prop]', 'propVal'],