Opencl datahandling

Since the target_dh_refactoring was never merged, we decided to do the refactoring at smaller steps and recover the original OpenCL datahandling PR.

Refactoring to merge target and backend can be done later.

conftest.py

@@ -33,7 +33,8 @@ def add_path_to_ignore(path):
     collect_ignore += [os.path.join(SCRIPT_FOLDER, path, f) for f in os.listdir(os.path.join(SCRIPT_FOLDER, path))]
 
 
-collect_ignore = [os.path.join(SCRIPT_FOLDER, "doc", "conf.py")]
+collect_ignore = [os.path.join(SCRIPT_FOLDER, "doc", "conf.py"),
+        os.path.join(SCRIPT_FOLDER, "pystencils", "opencl", "opencl.autoinit")]
 add_path_to_ignore('pystencils_tests/benchmark')
 add_path_to_ignore('_local_tmp')