Merge branch 'MC/volsrcs' into devel

doc/changelog.md

doc/lua_api.md

include/entity.h

include/gpu_support.hpp

include/kernels_gpu.h

include/maxwell_interface.h

src/entity.cpp

src/kernels_cuda.cu

src/maxwell_cpu.cpp

src/maxwell_gpu.cpp

src/maxwell_interface.cpp