Djsopnet: only have admin for config models
Djsopnet: fix too small stack ID input
Djsopnet: return null ID for missing objects

Do not return -1, which is a valid ID (though not in the default
sequence) for many models. Instead return null. In general the API
should indicate an object was not found with a status code, but this is
a temporary improvement to prevent attempting to fetch non-existent
objects from clients.
Djsopnet: add parameters for constraints

Constraints can now specify segment coefficients, inequality relation,
and value.