Squashed commit of the following:

commit ddc65f71
Author: David Hammer <dhammer@mailbox.org>
Date:   Wed Aug 25 16:58:47 2021 +0200

    Add individual source names to their metadata

commit 5ba47ce0
Author: David Hammer <dhammer@mailbox.org>
Date:   Wed Aug 25 16:48:12 2021 +0200

    Add metadata for control sources, too

src/calng/ShmemToZMQ.py

@@ -42,15 +42,6 @@ class ShmemToZMQ(PipeToZeroMQ.PipeToZeroMQ):
         new_meta = {}
         new_data = {}
 
-        # additional unstacked sources
-        if data.has("unstacked"):
-            for source in data.get("unstacked").getKeys():
-                forward, ignore = self._filter_properties(data, source)
-                new_data[source] = conversion.hash_to_dict(
-                    data.get(f"unstacked.{source}"), paths=forward, version=self.version
-                )
-            data.erase("unstacked")
-
         # stacked data from ModuleStacker
         for source, handle_string in zip(data.get("sources"), data.get("image.data")):
             if source not in self.sources:
@@ -64,6 +55,7 @@ class ShmemToZMQ(PipeToZeroMQ.PipeToZeroMQ):
 
             new_meta[source] = conversion.meta_to_dict(metadata)
             new_meta[source]["ignored_keys"] = ignore
+            new_meta[source]["source"] = source
 
             shmem_name, _, _, shmem_index = shmem_utils.parse_shmem_handle(
                 handle_string
@@ -105,6 +97,17 @@ class ShmemToZMQ(PipeToZeroMQ.PipeToZeroMQ):
             new_data[source] = (dic, arr)
             # note: assumes version "2.2" of the PipeToZeroMQ packing format
 
+        # additional unstacked sources
+        if data.has("unstacked"):
+            for source in data.get("unstacked").getKeys():
+                forward, ignore = self._filter_properties(data, source)
+                new_data[source] = conversion.hash_to_dict(
+                    data.get(f"unstacked.{source}"), paths=forward, version=self.version
+                )
+                new_meta[source] = conversion.meta_to_dict(metadata)
+                new_meta[source]["source"] = source
+            data.erase("unstacked")
+
         # forward data to all connected ZMQ sockets
         self._send(new_data, new_meta)