Safe margin property on CharacterBody only, used as argument in
move_and_collide.
Removed kinematic_safe_margin in 3D physics server, not really useful
and now harmonized with 2D.
- snap property to replace move_and_slide_with_snap()
- floor_max_angle, stop_on_slope, infinite_inertia, max_slides,
up_direction properties to replace arguments from move_and_slide()
- up direction now defaults to Vector3.UP and Vector2.UP
PhysicsBody now has methods move_and_collide/test_move and needed
properties for these methods: safe margin, locked axes (3D only).
Moved collision_exceptions from StaticBody to PhysicsBody for 3D
(same as 2D, and conforms to documentation).
RigidBody doesn't have test_motion method anymore, it's now redundant
with PhysicsBody.test_move.
