Bug 11343: The max number of items to process in a batch is hardcoded

Bug 11343: The max number of items to process in a batch is hardcoded

Until now, the maximum number of item records to process in a batch was
hardcoded to 1000.
This patch adds a syspref MaxItemsForBatch in order to allow to adapt
this value.

Test plan:
- set the pref to 2
- try to delete a batch of 3 items: they are not displayed
- try to modify a batch of 3 items: you are not allowed to do that
- set the pref to 1000 and try again. Now items are displayed and you
  are allow to modify them.

Signed-off-by: Christopher Brannon <cbrannon@cdalibrary.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>