WIP: Begin h5 cfood for unit tests

unittests/h5_cfood.yml

+---
+metadata:
+  crawler-version: 0.6.1
+---
+# Top-level, we have just the HDF5 file.
+H5FileElement:
+  type: H5File
+  match: (.*)\.(hdf5|h5)$
+  subtree:
+    # Here, we have the groups, the top-level dataset, and possible attributes
+    # (empty for now).
+    RootIntegerElement:
+      type: H5Dataset
+      match: ^root_integers$
+      records:
+        H5Dataset:
+          parents:
+            - H5Dataset
+      subtree:
+        # included NDArray in this dataset
+        TopLevelIntNDElement:
+          type: H5Ndarray
+          match: (.*)
+          recordname: this
+          records:
+            H5Dataset: +$this
+        # There is one more list-valued attribute to this dataset.
+        TopLevelDataAttribute:
+          type: ListElement
+          match: ^attr_data_root$
+          subtree:
+            AttributeListEntries:
+              type: FloatElement
+              match: (?P<value>.*)
+              records:
+                H5Dataset:
+                  attr_data_root: +$value
+            
+