Everything should be optional

[hobnob]

At the moment monsters have settings for the level they appear at to different party sizes (none, normal, elite). But some scenarios also apply a filter to items within the map depending on the party size. For example, Scenario 23 requires different pressure plates to be assigned depending on the party size.

We need a way of ascertaining that something is visible only to certain party sizes. The recomendation is 3 optional flags (twoPlayerVisible, threePlayerVisible, and fourPlayerVisible) in the scenario JSON on obstacles, traps, doors, etc. to determine visibility. by default these would be true but can be overridden in the JSON