I should be able to put a Photo in a Model Type

Summary: As with a number of other stories, this doesn't yet work because Photos aren't compatible with editInternal() -- they are special snowflakes.

This and the related stories are probably the straw that breaks the camel's back in terms of forcing me to refactor/rewrite/enhance editInternal() in several ways. We need to be able to rearrange and delete without sending the entire Lists back and forth -- indeed, without passing the entire object being affected, just some sort of handle. (Possibly generate a hash for each List element?)

We might replace the semantics of editInternal (which takes the entire new value) with finer-grained add/replace/delete/rearrange operations. This would be a huge win in many ways, but isn't trivial.

And we need to be able to plug a more-sophisticated body handler, like we are using in Photos, into the editInternal() powertrain.

Basically, editInternal() needs to become more pluggable and more general, which isn't going to be an easy task.