refactor(compiler): rename decorator directives into directive

BREAKING CHANGE:
Previously, `Directive` was the abstract base class of several directives.
Now, `Directive` is the former `Decorator`, and `Component` inherits from it.

modules/angular2_material/src/components/input/input.js

@@ -1,6 +1,6 @@
-import {Decorator} from 'angular2/src/core/annotations_impl/annotations';
+import {Directive} from 'angular2/src/core/annotations_impl/annotations';
 
-@Decorator({
+@Directive({
   selector: 'md-input-container input'
 })
 export class MdInput {
@@ -10,7 +10,7 @@ export class MdInput {
 }
 
 
-@Decorator({
+@Directive({
   selector: 'md-input-container'
 })
 export class MdInputContainer {