Changes:
-Added support for custom inertia and center of mass in 3D
-Added support for custom center of mass in 2D
-Calculated center of mass from shapes in 2D (same as in 3D)
-Fixed mass properties calculation with disabled shapes in 2D/3D
-Removed first_integration which is not used in 2D and doesn't seem to
make a lot of sense (prevents omit_force_integration to work during the
first frame)
-Support for custom inertia on different axes for RigidBody3D
When synchronizing CharacterBody motion with moving the platform using
direct body state, only the linear velocity was taken into account.
This change exposes velocity at local point in direct body state and
uses it in move_and_slide to get the proper velocity that includes
rotations.
For the time being we don't support writing a description for those, preferring
having all details in the method's description.
Using self-closing tags saves half the lines, and prevents contributors from
thinking that they should write the argument or return documentation there.
MODE_DYNAMIC instead of MODE_RIGID
MODE_DYNAMIC_LOCKED instead of MODE_CHARACTER
No more special case for sleeping behavior for MODE_DYNAMIC_LOCKED
(MODE_CHARACTER was forcing the body not to sleep, which is redundant
with can_sleep and wasn't done in Bullet).
