Add DataHandling.add_arrays

This adds a function for lazy people who want to write

dh = create_data_handling((20, 30))
x, y, z = dh.add_arrays('x, y(9), z')

instead of

dh = create_data_handling((20, 30))
dh.add_array('x')
dh.add_array('y', values_per_cell=9)
dh.add_array('z')

because in most cases you want to use more than one array.

pystencils/datahandling/datahandling_interface.py

@@ -62,7 +62,7 @@ class DataHandling(ABC):
             pystencils field, that can be used to formulate symbolic kernels
         """
 
-    def add_arrays(self, description: str):
+    def add_arrays(self, description: str) -> Tuple[Field]:
         """Adds multiple arrays using a string description similar to :func:`pystencils.fields`