It is a fast way to keep track of overlapping objects in an area, and doing rayTest and convexSweepTest for overlapping objects, instead of btCollisionWorld::rayTest/convexSweepTest.
Updated KinematicCharacterController to use btPairCachingGhostObject.
+ improved btSubsimplexConvexCast, btContinuousConvexCollision and btGjkConvexCast to support configuration that start in touching/penetration, required for 'sliding'.
+ added files to CMakeLists.txt for CharacterController
+ bump up version to 2.70 (preparation for beta)
