Fix bundling lazy load

[mgmarlow]

The Playground build script no longer creates a sandboxes.ts file in the user's directory. Instead, the compiled sandboxes.js is rewritten at runtime in the node_modules/angular-playground/dist/app/shared/ directory.

This fixes two issues:

1. Non-standard project paths no longer need to worry about the location of the sandboxes.ts file
2. Playground is back to chunking out each sandbox individually as intended