User activity tracking: open-ils.auth additions

User activity tracking: open-ils.auth additions

* Creates usr_activity entries for login and authentication verification
  requests

* Adds a new parameter to open-ils.auth.authenticate.[complete|verify]
  methods called "agent" which maps to the usr_activity column for "ewho"
  (the UI or 3rd-party that initiated the action).

* Adds a new API call "open-ils.auth.authenticate.verify", which behaves
  almost identically to authenticate.complete, with the exception that it
  does not "log in" (i.e. create an auth token and cache the user object).
  Instead, it simply returns a SUCCESS event if the username/barcode and
  password combination are valid.

Signed-off-by: Bill Erickson <berick@esilibrary.com>
Signed-off-by: Thomas Berezansky <tsbere@mvlc.org>