Add OpenProject template

Promotion: I'll mention it on Twitter and probably ping the OpenProject maintainers as I created the `openproject` image from scratch, so they might be interested in it.  I picked this project because my older brother is a project manager and he had expressed interest in trying this project out for professional reasons, but it was too hard for him to try and install it himself on a Linux server.  I'm hoping Panamax will make the process easier for him.