Derived units now use a DLUnit class similar to a DLPak to be easily
stored and loaded, the public API has been updated to either take a
DLUnit object or a Path where it reads the DLUnit from a *.dlunit file
The .dlunit file is a ZIP compressed archive containing two files, a
manifest.json which stores the units uuid, its input signals and its
output signal, and unit.py which is the python code for the unit, the
same rules apply (one python function with a specifically structured
signature) as when a string was passed in the old API
Errors have been added to have a DLUnitError similar to the DLPakError
as the DLUnit class is heavily inspired from the DLPak architecutre
Logging may still be primitive, this will be covered in the next AI
logging sweep to homogenize and clean up the logging aspect of things
