Warp cheat adjustments

• Warping to levels you haven't visited is now a cheat.
• Using -force with the map command only sets cheats if no other errors prevent the warp.
• No longer I_Error when trying to use -warp to a locked level -- now it just activates cheats.
• The exitlevel command is now a cheat when using it in Coop gametypes.
• Game clears only increment in Coop gametypes, instead of any gametype with cutscenes.
• Game clears don't increment if you failed the final stage.
• Fix stagefailed for intermission Lua hooks not working outside of Special Stages.