LP#2009725 Place holds for recent patrons

LP#2009725 Place holds for recent patrons

Adds a button to the holds interface to retrieve the last patron
or show a dialog of recent patrons depending on the Number of
Retrievable Patrons org unit setting.

When a patron is loaded in the holds interface, they are added
to the recent patrons list.

- If the Number of Retrievable Recent Patron setting is < 1,
  the button doesn't appear.

- If the setting is 1 or unset (1 is default), clicking loads
  the last patron.

- If the setting is greater than 1, clicking shows a dialog of
  recent patrons to select from.

- If there are no recent patrons, the button is disabled.

Signed-off-by: Dan Briem <dbriem@wlsmail.org>