add feature of computing energy

src/BrownianParticleType.cpp

src/BrownianParticleType.h

src/ComputeForce.cu

src/ComputeForce.cuh

src/ComputeForce.h

src/ComputeGridGrid.cu

src/Configuration.cpp

src/GrandBrownTown.cu

src/GrandBrownTown.cuh

src/RigidBody.cu

src/RigidBodyController.cu

src/TabulatedMethods.cuh

src/useful.cu

src/useful.h