Fix sector special definitions and restore flags under ZDoom.

- Sector specials were slightly incorrect: a couple were misnumbered, some "leaked" from the game definition into the port definition, they weren't cleared between configuration reloads, and Strife was just using Doom's.  They should now, hopefully, match [the original games' sector types](http://doomwiki.org/wiki/Sector#Sector_types) and [ZDoom's definitions](https://github.com/rheit/zdoom/tree/master/wadsrc/static/xlat).

- Disabling Boom extensions for Hexen/UDMF maps in ZDoom meant the Boom sector flags vanished from the sector special panel.  I put them back by using a separate configuration twiddle, which also removes all the special-casing for map format.

- The propgrid now shows the name of a sector special.