Bug 9209 - Mocked Koha::Calendar tests

Bug 9209 - Mocked Koha::Calendar tests

Using specific method for populating the internal data structures from Koha::Calendar
has yielded to the non-detection of several bugs. There are also several tests that where
db_dependent which is not always desirable.

I propose the use of DBD::Mock (::Session) for using the actual code used by Koha in production
for testing, mocking the DB queries itselves.

I also took the time to repeat several tests in different syspref configurations (they applied
only to daysMode=Calendar, and now cover all confs).

Notes:
- I used DBD:Mock 1.45 as previous version (1.43, from 12.04) was broken
- Some tests revealed a bug on days_between as I see it... reporting as Bug #9211

Sponsored-by: Universidad Nacional de Córdoba
Signed-off-by: Elliott Davis <elliott@bywatersolutions.com>
Signed-off-by: Jared Camins-Esakov <jcamins@cpbibliography.com>