Bug 7413: Code and intranet template changes

Bug 7413: Code and intranet template changes

This patch modifies CanBookBeRenewed, so that based on
issuingrules.norenewalbefore a new error "too_soon" can be returned.
Also adds a new subroutine GetSoonestRenewDate.

To test:
1) Create an issuing rule with "No renewal before" set to value X
   and "Unit" set to days.
2) Test the following steps for both:
   Home > Patron > Patron details
   Home > Circulation > Checkouts
3) On the checkout page, test for today's issues as well as previous
   issues. (Check something out on one day and something else on the
   next day, then do the testing.)
4) Confirm that items can't be renewed if current date is more than
   X days before due date.
5) Confirm that the date and time of the soonest possible renewal are
   displayed in the format specified by global sysprefs "dateformat"
   and "TimeFormat".
6) Confirm that items can be renewed if "No renewal before" is
   undefined or current date is X or less days before due date.
7) Confirm that if the number of allowed renewals is exceeded
   "Not renewable" is displayed, no matter what "No renewal before"
   is set to.
8) Test the same things with "Unit" set to hours.

Sponsored-by: Hochschule für Gesundheit (hsg), Germany
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Brendan Gallagher <brendan@bywatersolutions.com>