This doesn't make much sense API-wise, but it's important for the documentation
workflow that the Mono and non-Mono builds produce the same output, otherwise
we keep having non-Mono builds removing Mono properties and losing their
descriptions.
This is a terrible hack but it's ad hoc, and should be OK for the time being.
Now that the unused DocDump was removed, the `editor/doc` subfolder is
redundant.
Similarly, there's no reason for Collada to have a subfolder for itself
when glTF or OBJ don't.
