Issue #292 and related to issue #195 . Considered update and create events as different cases. If updated, check all visit_numbers. Added tests accordingly

Issue #278 Avoid deleting availabilities from the daily planning and add more control for undefined values

Issue #195 added tests and changed the post_save function for visit. I didn't saw a problem of concurrency but a problem of saving the visit accordingly. Maybe we need more tests

Issue #276 changed check_nd_number_regex to receive a study and to filter out null or blank nd_numbers in the studySubjects

Fixed problem when the window was to small.
Moved the creation of the daily planning to a separate function, allowing for custom properties and also total override of the daily planning default properties.

Issue #266 Fixes problem when no voucher is checked to be printed. Rises a tooltip. But, even if the call was produced and no template was found in generate_for_vouchers, it would be redirected to the previous page (subject edit) or, if no previous page is found, to the subject list