+ make compound versus soft body work (soft body uses interpolated transform)

+ fixed issue with persistent manifold, warmstarting values were not initialized properly
+ don't clear manifold in sphere-sphere collision (need warmstarting)
+ added support for 'split impulse', decouple positional error correction from velocity correction
This avoids adding momentum due to penetration correction, it can be tuned using following variables:
solverInfo.m_splitImpulse = true/false (disable/enable)
solverInfo.m_splitImpulsePenetrationThreshold (below this value, baumgarte/mixed velocity/penetration is used (cheaper, looks more plausible)
solverInfo.m_linearSlop (less jitter, when small amound of penetration is allowed)

src/BulletCollision/NarrowPhaseCollision/btPersistentManifold.cpp

@@ -183,7 +183,8 @@ void btPersistentManifold::AddManifoldPoint(const btManifoldPoint& newPoint)
 
 		
 	}
-	replaceContactPoint(newPoint,insertIndex);
+	btAssert(m_pointCache[insertIndex].m_userPersistentData==0);
+	m_pointCache[insertIndex] = newPoint;
 }
 
 btScalar	btPersistentManifold::getContactBreakingThreshold() const