Comment 4 for bug 830309

@yman, yes, after another brief discussion we'll probably do as you suggest:

1. The first seven bullets of comment #3 still apply.
2. The UI for creating a demo will be part of the initial app submission workflow. On the first screen, where you upload the package, you'll have an option to provide a demo for the app.
3. The demo package should be mentioned on the details page in the "Your app" section, displaying just the uploaded demo package.
4. Reviewers will have to upload the demo and full versions of the app to separate ppas, so they'll need separate archive id, signing key and package name fields for each.
5. You should be able to submit an app for review even if it *only* has a demo version. This will allow devs that haven't yet completed the details for the full version of an app to still start generating a bit of hype around their app, by providing a demo.
6. If an app only has a demo version (no full version), once published the available-apps-for-purchase api call will include the details for the demo package and just leave the current package_name, archive_id and signing_key fields empty.
7. The client should be able to handle this case, by graying out the "Purchase" button, possibly giving an explanation (eg "Not available yet"), and providing a button to install the demo version.