Remove these unused props_*.cfg files.
One more unused config file!
Prop grid now manages args for both thing type and special.

This makes arg labels do more or less what you'd expect when mucking
with a thing's type and special.

Also fixed the ZDoom configuration so that a thing's type is actually
defined as such, and the [...] button works correctly.
Don't reload the property grid when toggling "show all".

I've lost work this way!  Instead, ask each property to decide whether
it should be visible now.
Really not feeling vector::begin/end.
Use a combobox for string properties with values, like renderstyle.
Merge pull request #126 from eevee/propgrid-config-harmony

Joint config/propgrid fixes.