Bug 8365: Add a renewal duration in the issuing rules

Bug 8365: Add a renewal duration in the issuing rules

Renew an issue for a number of days (filled in the issuing rules).

Test if rules work for any i[item]types and if there is no regression.

- new column issuingrules.renewalperiod
- remove all occurrences of an already removed syspref (globalDueDate)
- remove an unused routine (Overdues::GetIssuingRules)

How it works:
- On existing installations, the issuingrules.renewalperiod =
  issuingrules.loanlength. So the behaviour is the same before and after
  this patch.
- when you add a rule, you can choose a renewal period (the unit value
  is the issuingrules.unit). So you can have a renewal period in hours
  or days.
- The default value for the renewal period is 21 days (same as
  loanlength)

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
Test comments on second patch.
Signed-off-by: Jared Camins-Esakov <jcamins@cpbibliography.com>