refactor(pipes): rename PipeRegistry to Pipes

BREAKING CHANGE:
    This change renames all instances of PipeRegistry to Pipes.
    As part of this change, the former "defaultPipes" export is
    now a Pipes instance, instead of a map. The map that was previously
    called "defaultPipes" no longer exists, but may be accessed via
    defaultPipes.config.

modules/angular2/angular2.ts

@@ -14,14 +14,13 @@ export {
 
   ChangeDetectorRef,
 
-  PipeRegistry,
+  Pipes,
   WrappedValue,
   Pipe,
   PipeFactory,
   NullPipe,
   NullPipeFactory,
   defaultPipes,
-  defaultPipeRegistry,
   BasePipe,
 
   Locals