make it valid to not have a valid org name/guid
remove unused export admin_field_is_false
allow create_from_json to handle objects when no org id is present
only define migration and default hash types if they haven't been at a higher level

* Note use of atom_to_binary came about because rebar define directives
  cause an internal compile error when binary values were used.
Merge pull request #108 from opscode/mp/user-endpoint

Note that compatible chef_wm is now under branch "mp/users-lock", which erchef has been configured to use for OSC.