Makes the API for forces and impulses more flexible, easier to
understand and harmonized between 2D and 3D.
Rigid bodies now have 3 sets of methods for forces and impulses:
-apply_impulse() for impulses (one-shot and time independent)
-apply_force() for forces (time dependent) applied for the current step
-add_constant_force() for forces that keeps being applied each step
Also updated the documentation to clarify the different methods and
parameters in rigid body nodes, body direct state and physics servers.
Damping values are now non-negative.
Add new properties linear_damp_mode and angular_damp_mode to set the way
RigidDynamicBody and PhysicalBone (2D & 3D) use damping values.
It can now be Combine (default) to add to the default/areas, or Replace
to override the value completely (current behavior).
Fix some typoed names from the doc
Add _index to "index" parameters of *_shape_* signals, this is both in doc and in the template. This makes the code, signature and doc easier to understand
Add method to get Node from the _index params of those signals. This was not as easy to find as one would expect. Putting this information where it is needed will help.
RigidDynamicBody modes are replaced with several properties to make their
usage clearer:
-lock_rotation: disable body's rotation (instead of MODE_LOCKED)
-freeze: no gravity or forces (instead of MODE_STATIC and MODE_KINEMATIC)
-freeze_mode: Static (can be only teleported) or Kinematic (can be animated)
Also renamed MODE_DYNAMIC_LOCKED to MODE_DYNAMIC_LINEAR in the physics
servers.
