With splitting DMF and DML, there is now more than one case where this
is needed, so it may well be made proper now.
The template still defines them, and, as with VT2 most creators will
probably stick with it, but they do have the option to make a non-DMF
mod now.
There are a bunch of optional commands provided by druid that trigger
this, but we only really need it to check for custom ones that weren't
implemented, yet.
Ditch the `.mod` file and move its data into the config file.
The `run` function was the only thing that could have been dynamic, but
the vast majority of mods in VT2 never made use of that. Infact, VMF was
probably the only mod that had a different content for that.
