Bug 23208: Add ability to set a default hold ratio value

Bug 23208: Add ability to set a default hold ratio value

To test:
1. APPLY PATCH, updatedatebase, restart_all
2. Search for the system preference 'HoldRatioDefault'.
3. It should be set to 3. Change the value to something else.
4. Load the report at 'circ/reserveratios.pl'. Circulation > Hold ratios
5. The default value should be the value you set in the new system preference.
6. Run the report with the default value and make sure it works.
7. Change the value and run the report. The new value should be retained.
8. Leave the page and come back. Again the default value from the new system preference should be set.

Signed-off-by: Andrew Fuerste Henry <andrewfh@dubcolib.org>
Signed-off-by: Emily Lamancusa <emily.lamancusa@montgomerycountymd.gov>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>