Started introducing source-sets to play component model

- Added sourceSet for generated scala sources
  - This allows separate configuration of twirl/routes compile tasks from scala compile task
- Introduce (untyped) source set for app scala sources
  - This separates configuration of source directories from task configuration
  - Not yet user configurable (later story)
Configure application sources on PlayApp component instead of PlayApp binary
Fix the ‘play new’ sample to match what is actually created