Added __param helper for parameter decorators and cleaned up __decorate and __metadata

src/compiler/commandLineParser.ts

@@ -156,6 +156,11 @@ module ts {
             shortName: "w",
             type: "boolean",
             description: Diagnostics.Watch_input_files,
+        },
+        {
+            name: "emitDecoratorMetadata",
+            type: "boolean",
+            experimental: true
         }
     ];