Portals - Autoplacing static objects and further work

[lawnjelly]

In order to make level building easier, the system can now support STATIC and DYNAMIC objects in the roomlist that are not placed in rooms. The system will automatically place them in the appropriate room.

• Lifts restrictions now allowing the RoomManager to be the roomlist.
• Fixes a couple of bugs which could occur if the user attempted to link Portals to Rooms that were outside the roomlist.
• Adds a PortalEditorPlugin allowing you to flip individual portals.
• Add support for MultiMeshInstance in calculating room bound.

Notes

• This should prove a lot easier to use for users. Instead of placing all objects within each room, they only need to make sure the Room bound is defined (either by placing walls and floor in the room, or manual bound), and that Portals are placed in the Room. Other objects can be placed freely within the roomlist (not in rooms) and they will be autoplaced during conversion.
• Autoplacing does not change their position in the scene tree, it just changes how they are structured in the portal renderer.
• Autoplaced nodes cannot affect the room bounds (hence why you need to place walls etc explicitly in the room if you are deriving the bound from the geometry)
• It should work in most cases and uses the AABB centre to determine which room to put in
• It is not guaranteed to work with internal rooms. It will attempt to choose the highest priority internal rooms and will work in 95% of cases, but there are some special cases for large objects that sprawl outside internal rooms (see the portal instructions) and these should be placed manually in the rooms in the scene tree rather than relying on autoplace.
• At the moment autoplaced objects will not be merged (static batching) if you have that option selected. I may be able to get this to work in a later PR.

[akien-mga]

Thanks!