Added derive units to core

Derive units are now available in the core and has their relevant input
values routed and outputs are looped back into the core router

Fixed the dlpak manifest which had no signal descriptors

src/dynalab_core/buffer.py

@@ -32,6 +32,8 @@ class ValueBuffer:
             return len(self._samples)
 
     def normalize(self) -> None:
+        if len(self) == 0:
+            return
         with self._lock:
             minimum = min(sample[0] for sample in self._samples)