added assertions on kernel argument, added capability to alter kernel during autotuning

hysop/__init__.py

hysop/backend/device/autotunable_kernel.py

...p/backend/device/codegen/kernels/directional_advection.py

hysop/backend/device/codegen/kernels/directional_remesh.py

hysop/backend/device/codegen/kernels/transpose.py

hysop/backend/device/kernel_autotuner.py

...ackend/device/opencl/autotunable_kernels/advection_dir.py

...p/backend/device/opencl/autotunable_kernels/remesh_dir.py

hysop/backend/device/opencl/autotunable_kernels/transpose.py

hysop/backend/device/opencl/opencl_autotunable_kernel.py

hysop/backend/device/opencl/opencl_env.py

hysop/backend/device/opencl/opencl_kernel_autotuner.py

hysop/backend/device/opencl/opencl_kernel_launcher.py

hysop/backend/device/opencl/operator/transpose.py

hysop/operator/tests/test_directional_advection.py