chore(bundle): avoid imports in "global" format

If an "empty" file (like angular2/template.js) is imported
it is auto-detected as the one using "global" format by the
system builder. This is incorrect as the entire angular2 build
output is in the ES6 format.

Removing empty import till it has some content.

Closes #1329

modules/angular2/angular2.js

@@ -1,6 +1,5 @@
 export * from './change_detection';
 export * from './core';
 export * from './annotations';
-export * from './template';
 export * from './directives';
 export * from './forms';