Basic destructuring support

[vemv]

Different from nedap/utils.spec#13

The following doesn't work:

(speced/defn update-default-applications! [this
                                           ^::protocols.edit/update-default-applications
                                           {:keys [org-id application-id enabled?] :as input}]
  (println input))

...since the spec failure will have the following form:

-- Spec failed --------------------

  {:as {:org-id 9999123, :application-id 2, :enabled? true},
   :keys [9999123 2 true]}

should contain keys: :application-id, :enabled?, :org-id