Move group file and update headers

Src/GroupTree/Core/FGroupAttachedLeaf.hpp

Src/GroupTree/Core/FGroupOfCells.hpp

Src/GroupTree/Core/FGroupOfParticles.hpp

Src/GroupTree/Core/FGroupSeqAlgorithm.hpp

Src/GroupTree/Core/FGroupTaskAlgorithm.hpp

Src/GroupTree/Core/FGroupTaskDepAlgorithm.hpp

Src/GroupTree/Core/FGroupTaskStarpuAlgorithm.hpp

Src/GroupTree/Core/FGroupTaskStarpuMpiAlgorithm.hpp

Src/GroupTree/Core/FGroupTree.hpp

Src/GroupTree/Core/FOutOfBlockInteraction.hpp

Src/GroupTree/Core/FP2PGroupParticleContainer.hpp

Src/GroupTree/Cuda/FCudaDeviceWrapper.hpp

Src/GroupTree/Cuda/FCudaEmptyCell.hpp

Src/GroupTree/Cuda/FCudaGroupOfCells.hpp

Src/GroupTree/Cuda/FCudaGroupOfParticles.hpp

Src/GroupTree/Cuda/FCudaStructParams.hpp

Src/GroupTree/OpenCl/FEmptyOpenCLCode.hpp

Src/GroupTree/OpenCl/FOpenCLDeviceWrapper.hpp

Src/GroupTree/StarPUUtils/FStarPUCpuWrapper.hpp

Src/GroupTree/StarPUUtils/FStarPUCudaWrapper.hpp