Togglable collision for PhysicsBody

[avahe-kellenberger]

I've ran into a use case (in Hexagone) where disabling collision checks for a PhysicsBody would be useful.

There are one or two "work-arounds" for this problem, but being able to disable the check simply and altogether would be beneficial.

[avahe-kellenberger]

An alternate solution which may be more beneficial, is to implement collision masks (similar to Godot). With all bits set to 0, the object would not be able to collide with any other object.