(bug 1532) Reserves Updates Ported From Dev_Week

(bug 1532) Reserves Updates Ported From Dev_Week

This is a much improved re-implementation of the reserves updates from dev_week.
Less new code has been added, and more existing functions are used instead of adding new ones.

The 'Lock Hold' function has been removed due to it not working as intended.

[RM note for documentation: this adds the following features:

* ability to specify an expiration date for a hold request
  when placing it via the staff interface or OPAC
* daily batch job to cancel expired holds
* nice interface to change the priority of hold
  requests for a bib in the staff interface]

Signed-off-by: Galen Charlton <gmcharlt@gmail.com>