Bug 33945: Add ability to delay the loading of the current checkouts table on the...

Bug 33945: Add ability to delay the loading of the current checkouts table on the checkouts page

If a librarian has opted to load the checkouts table automatically on the checkouts page, it will trigger a call to svc/checkouts. If a librarian is checkout out 10 items to a patron, that means svc/checkouts is called uselessly 9 times, with only the 10th time being used to display the checkouts table.

It would be useful to add a delay such that the table only load if the page has been display for a given number of seconds. That way the continuous scanning does not trigger useless svc/checkouts calls, but the librarian also does not need to click the load checkouts button manually.

Test Plan:
1) Apply this patch
2) Run updatedatabase.pl
3) Verify "Always show checkouts immediately" retains its' original
   behavior of loading the checkouts table immediately
4) Set LoadCheckoutsTableDelay to a non-zero integer
5) Verify the automatic table loading is delayed by that number of
   seconds

Signed-off-by: Sam Lau <samalau@gmail.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>