Clean up engine/DynamicsWorld.java
Clean up engine/ContactSolver.java
Clean up engine/ContactPointSolver.java
Clean up engine/ContactManifoldSolver.java
Clean up engine/ContactManifold.java
Clean up engine/ConstraintSolverData.java
Clean up engine/ConstraintSolver.java
Clean up engine/CollisionWorld.java. This should be the last file except for the joint classes.