Multi-level static camera export option

Add an option to export a multi-level map without adjusting the height of the camera between each level of the map. Would be helpful for making multilevel maps with e.g. the Levels module for Foundry. Currently, graphics do not fully align due to camera moving slightly up at each level, requiring resizing in an image editor followed by moving exported walls, etc.

Would be problematic for particularly tall maps, so would be best as an optional export feature.