Add an output format 'image'

In order to know the content type to send, we need to have the completed object accessible via the OutputController, so the index and output controller were modified to account for that.
Use the image model

But add a legacy route.
Implement the Image model

It looks like what was there was a 'best guess'.  Because it was extending an event, and $this->reload() was being called in the constructor, it would end up in an infinite loop.  It is better to not extend record classes for this reason.
Add image templates