now that barrel reorg is done and bundle reorg is almost done, it is time to remove the angular2/angular2 barrel (entry point) and force everyone to import from the correct location.

We are doing this because of the rule to export each symbol only via one public entry point to prevent confusion and code portability issues due to duplicate/platform-specific/bundle-specific imports.

This change will affect the following:

• remove angular2.ts
• remove angular2.dart - requires fixing g3, so we should just fix ts side and leave this item open if we need more time to fix g3 refactor: deprecate angular2/angular2 import for dart #4027
• update all internal imports that depend on angular2/angular2
• update System.register bundle config
• update UMD bundle config
• update all api docs
• update all dev guide docs
• update all dgeni (doc generation) entry points
• update cli blueprints
• update seed

// @pkozlowski-opensource @vsavkin @robwormald @wardbell @yjbanov @petebacondarwin