handle partial API POST and PUT requests

[gassc]

Need add'l logic and tests to make sure that the API methods can handle partial submissions, and elegantly fill in the blanks for non-mandatory fields. I think right now it might be rejecting anything less than a full fish fry feature.

[gassc]

I've sorted out how to do this, with the generous help of Stack Overflow:

def deep_merge(d, u):
   """Do a deep merge of one dict into another.
   This will update d with values in u, but will not delete keys in d
   not found in u at some arbitrary depth of d. That is, u is deeply
   merged into d.
   Args -
     d, u: dicts
   Note: this is destructive to d, but not u.
   Returns: None
   """
   stack = [(d,u)]
   while stack:
      d,u = stack.pop(0)
      for k,v in u.items():
         if not isinstance(v, collections.Mapping):
            # u[k] is not a dict, nothing to merge, so just set it,
            # regardless if d[k] *was* a dict
            d[k] = v
         else:
            # note: u[k] is a dict

            # get d[k], defaulting to a dict, if it doesn't previously
            # exist
            dv = d.setdefault(k, {})

            if not isinstance(dv, collections.Mapping):
               # d[k] is not a dict, so just set it to u[k],
               # overriding whatever it was
               d[k] = v
            else:
               # both d[k] and u[k] are dicts, push them on the stack
               # to merge
               stack.append((dv, v))

This would happen somewhere in db_interface.py