Include the expert app in the public docker image

Addresses the fact that the expert-app doesn't currently run on the public CARA docker image. This was based on feedback from a user on Monday.

The static file handling can still be improved (i.e. no 404s, and showing the logo) for both this case, and the main cara expert-app on the website, I don't propose to address that issue here (it is painful, and somewhat relates to #180 (closed)). The docker image testing continues to be weak, as per #186 (closed) - I don't have the time to work on that presently.