Update to v1.6

The mod is now update to v1.6! This is a very small update, it only changes two small things:

• The mod now has its own COMPLVL lump! Basically this ensures the mod will work in any mapset which sets its compatibility level to anything other than MBF21 - previously the mod would break on any map that didn't lock itself to MBF21.
• The PNG graphics are replaced by paletted PNGs, meaning you can use the mod with any map that has its own custom palette and the graphics will be preserved far better. Use this in GZDoom, Woof! or Nugget Doom.