WIP: Graph datahandling

This is the draft for a data handling that (optionally) forwards all calls to SerialDatahandling. All calls and data transfers get recorded for the creation of an execution graph.

Needs to be changed after the breaking changes in datahandling.

Needs a tiny change in lbmpy:

Instead of using TimeLoop(...) for time loop creation a custom function is used.

pystencils/datahandling/pyopencl.py

@@ -14,7 +14,8 @@ class PyOpenClArrayHandler:
         if not queue:
             from pystencils.opencl.opencljit import get_global_cl_queue
             queue = get_global_cl_queue()
-        assert queue, "OpenCL queue missing"
+        assert queue, "OpenCL queue missing!\n" \
+            "Use `import pystencils.opencl.autoinit` if you want it to be automatically created"
         self.queue = queue
 
     def zeros(self, shape, dtype=np.float64, order='C'):