Joint config/propgrid fixes.

- I found more unused config files!
- Thing's type is now correctly flagged as `thingtype`, and the arg code has been refiddled to make thing type play well with action special.  Should do what you'd expect: checks for thing type, then for special, then falls back to "arg1" etc.
- The property grid no longer calls `openObjects` when toggling the "show all" checkbox, after I lost a few changes by doing that.
- `renderstyle` shows as a combobox containing `translucent` and `add`.

I think I've run out of invasive things to do to propgrid now.  Probably.