Improve loaderupdate:Devices
Improve loaderupdate:Devices

Change the list structure to be able to contain an empty list.
As a side effect this adds the option of creating a partial list
with invalid devices being discarded, provided the list is constructed
in an error handling context (see ref/bsda_err.md).

lonkamikaze/bsda2,lonkamikaze/bsda2