phase 3 removing tbc

Drop the now-vestigial expansion plumbing.

- Delete modules/thirdparty-tbc.lua + its xml Include
- Strip 10 tbc-tagged CreateConfig calls in modules/gui.lua
- Drop the expansion arg from CreateConfig() signature + the disabled-
  entry rendering path that depended on it
- Drop the showdisabled GUI toggle + its default
- Simplify pfUI:RegisterModule / pfUI:RegisterSkin to (name, func) only
- Strip the leading version arg ("vanilla:tbc", etc.) from all 114
  Register call sites
- Delete the pfUI.expansion variable

modules/superwow.lua

@@ -38,7 +38,7 @@ SlashCmdList["PFDLLSTATUS"] = function()
   end
 end
 
-pfUI:RegisterModule("superwow", "vanilla", function ()
+pfUI:RegisterModule("superwow", function ()
   if SetAutoloot and SpellInfo and not SUPERWOW_VERSION then
     -- Turn every enchanting link that we create in the enchanting frame,
     -- from "spell:" back into "enchant:". The enchant-version is what is