Added btNearCallback. This is similar to Open Dynamics Engine (ODE) dNearCallback, but important differences:

- contact points are persistent (lifetime more then one frame, for warmstarting/incremental contact point management)
- continuous collision detection, time of impact
Added btRigidBody::isInWorld(), returns true if btRigidBody is inside a btCollisionWorld/btDynamicsWorld derived class
Added angularFactor to btRigidbody, this helps some character control (no angular impulse applied)

src/BulletDynamics/Dynamics/btRigidBody.cpp

@@ -35,6 +35,7 @@ btRigidBody::btRigidBody(float mass, btMotionState* motionState, btCollisionShap
 	m_totalTorque(0.0f, 0.0f, 0.0f),
 	m_linearVelocity(0.0f, 0.0f, 0.0f),
 	m_angularVelocity(0.f,0.f,0.f),
+	m_angularFactor(1.f),
 	m_linearDamping(0.f),
 	m_angularDamping(0.5f),
 	m_optionalMotionState(motionState),