Serve media data for public sites without authentication

[Alan Noble]

The getHandler method, which serves media data, currently performs user authentication.
It would be useful if media data for public sites could be served without the need for a logged-in user.

[Alan Noble]

Implemented in https://bitbucket.org/ausocean/vidgrind/commits/cda7437731ffe4c0d9f01308526a9629c4222a4f