feat(package): introduce a catch-all package angular.

modules/angular has no implementation, but depends on all the pieces
that make angular - core, di, directives, etc. It is the package that
all client apps will depend on.

modules/core/src/core.js

@@ -1,17 +1,12 @@
-/**
- * Define public API for Angular here
- */
 export * from './annotations/annotations';
 export * from './compiler/interfaces';
 export * from './annotations/template_config';
 
 export * from './application';
 
-export * from 'change_detection/change_detection';
-
 export * from './compiler/compiler';
 export * from './compiler/template_loader';
 export * from './compiler/view';
 export * from './compiler/viewport';
 
-export * from 'core/dom/element';
+export * from './dom/element';