cuda: major rewrite

labs/cuda/Makefile

labs/cuda/README.md

labs/cuda/arch/README.md

labs/cuda/arch/exercises/benchmark/Makefile

labs/cuda/arch/exercises/matrix_multiply/Makefile

labs/cuda/arch/tutorials/debug/Makefile

labs/cuda/arch/tutorials/debug/README.md

labs/cuda/arch/tutorials/timing/Makefile

labs/cuda/arch/tutorials/timing/README.md

labs/cuda/arch/tutorials/timing/cpu_timing/.gitignore

labs/cuda/arch/tutorials/timing/cpu_timing/Makefile

labs/cuda/arch/tutorials/timing/cpu_timing/cpu_timing.cu

labs/cuda/arch/tutorials/timing/events_timing/.gitignore

labs/cuda/arch/tutorials/timing/events_timing/Makefile

...cuda/arch/tutorials/timing/events_timing/events_timing.cu

labs/cuda/hello/.gitignore

labs/cuda/hello/Makefile

labs/cuda/hello/hello.cu

labs/cuda/intro/README.md

labs/cuda/intro/exercises/indices/Makefile