Fix licensing

LICENSE.txt

src/Makefile

src/backend.hpp

src/backend/distributed.cpp

src/backend/distributed.hpp

src/backend/simple.cpp

src/backend/simple.hpp

src/backend/tiled.cpp

src/backend/tiled.hpp

src/cifar10.cpp

src/core.hpp

src/kernels/conv_relu_fwd.cpp

src/kernels/conv_relu_fwd.hpp

src/kernels/kernels.hpp

src/mmap.cpp

src/mmap.hpp

src/nst.cpp

src/nst.hpp

src/nst_model/fp32_mac.cpp

src/nst_model/fp32_mac.hpp