Clarify item_request(), add missing $U

First, we clarify the item_request() sub by:
 - adding customization notes
 - making sure we retain our custom status after hold placement
 - identifying Item vs User Agency code branches

Second, we add the common $U AppUtils variable which was missing from
the last commit.

Signed-off-by: Dan Wells <dbw2@calvin.edu>
Remove force-to-available code from check_in_item

check_in_item() currently tries to force the checked-in copy to the
"Available" status.  This seems unnecessary, and possibly damaging.

Instead, let the EG check in process set the status as it sees fit
(most often to "Reshelving").

Signed-off-by: Dan Wells <dbw2@calvin.edu>
More customization markers, and general cleanup

First, add more CUSTOMIZATION markers wherever a value likely needs
per-system configuration.

Second, clean up and clarify the code in a few places.  This includes
standardizing some variable names.  In particular, $visid and
$barcode were both used interchangeably, and this commit standardizes
on $visid for anything which isn't an actual local item barcode (i.e.
it is a fake or external system "barcode" value).

Signed-off-by: Dan Wells <dbw2@calvin.edu>
A little defensive coding around last_post.txt.

If the file doesn't exist, rather than die, try to create it.  Only
die if we fail to create it.

Signed-off-by: Jason Stephenson <jstephenson@mvlc.org>
Merge pull request #3 from Dyrcona/last_post

A little defensive coding around last_post.txt.