Copy Location Search Groups : TPac org unit selector

Copy Location Search Groups : TPac org unit selector

Adds support for viewing and searching on copy location groups in the
tpac.  Groups appear within the org unit selector, when the selector is
used in a search context.  Groups display below the owning org unit
similar to a child org unit.  Groups are displayed for all org units
that meet the following criteria:  search org unit, physical location,
patron home org unit, plus ancestors and descendents of each.

To support this, TPac gets a new "locg" CGI parameter, which contains
the org unit and copy location group.  It takes the form
org_id:group_id.  The TPac mod_perl code will extract this value and
popuplate the search_ou accordingly.  For consistency, we also use
ctx.search_ou instead of directly checking CGI.param('loc') within the
template environment.

This also includes a rewrite of the org_selector.tt2 template.  It
changes it from a recursive routine to a depth-first while loop.  I did
this mainly because the recursive approach was suffering from global
variable clobbering in the template environment.  In theory, this new
approach should be faster as well.

Signed-off-by: Bill Erickson <berick@esilibrary.com>