Bug 30901: Add Renewals method to CirculationRules template plugin

Bug 30901: Add Renewals method to CirculationRules template plugin

It would be useful to be able to report renewals used/remaining in some notices and slips.

Test Plan:
1) Apply this patch
2) Add the following to the RENEWAL notices:
--
[% USE CirculationRules %]
[% SET renewals = CirculationRules.Renewals( borrower.id, item.id ) %]
You have used [% renewals.count %] of [% renewals.allowed %], you have [% renewals.remaining %] renewals left.
--
3) Trigger a renewal notice
4) Verify the text is correct!

Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>