Add map filters

[narfman0]

Add filters in the level so that the user can only see npcs, paths, polygons, joints, or whatever they are interested in. Somewhere there could be a list of all the modes and if they should be rendered. This could be part of an overall level preferences ui (for setting other things, like changing .preferences files on the fly or similar) or just a checkbox by each mode signifying if it should be rendered/filtered or not