Bug 36476: Add holds priority column to members/summary-print.pl pending holds table

Bug 36476: Add holds priority column to members/summary-print.pl pending holds table

To test:
APPLY PATCH and restart_all
1. Have a patron with and some holds and different priority.
2. Go to the patron account and click Print > Print summary
3. Notice the new holds priority column.

Note: Table settings don't work on these tables. See Bug 36475.
Signed-off-by: Sam Lau <samalau@gmail.com>
Signed-off-by: Matt Blenkinsop <matt.blenkinsop@ptfs-europe.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>