Feature/multiplayer things spawn options

[UnreallyHard]

Option is available for all netgame types Added Multiplayer Things Spawn Type to setup menu Added Cmd Line Parameter mpspawntype Added netgame functionality Added mobjtype_weapons array is_weapon function Closes https://github.com/fabiangreffrath/crispy-doom/issues/681

Options for Multiplayer Things Spawn Type are:

• All (0) - Default
• All except weapons (1) - The most often asked variant, ex. https://github.com/fabiangreffrath/crispy-doom/issues/681
• Only monsters (2) - One step further. Nothing multiplayer related is spawned except monsters. This option can be used to remove mp only ammo spawns
• None (3) - Nothing multiplayer related is spawned at all