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/errors.py

@@ -11,6 +11,10 @@ class CoreStateMismatchError(CoreError):
     """DynaLab Core state error."""
 
 
+class CoreMultipleFunctionsFoundError(CoreError):
+    """DynaLab Core multiple functions found while trying to create derive unit."""
+
+
 # DLPak error declarations
 class DLPakError(Exception):
     """DLPak error."""