[STORY] As a programme coordinator, I want to immediately de-activate and re-activate shows

Parent: [EPIC] Extend Show Management Area and improve ... (#149 - closed)

Currently, when a show is created, by default it is marked as active and is therefore visible in the dashboard.

Programme coordinators should be able to de-activate and re-activate a show.

Deactivating a show affects the Show instance and disables interaction with it in the Dashboard. It should affect Schedule and indirectly Timeslot instances:

• the show is marked as not active.
• existing schedules with last_date unset or after the current date should be set to the current date
• existing timeslots with start after the current date and time should be deleted as a consequence of updating the schedule.

Re-Activating a show affects only the Show instance and re-enables interaction with it in the Dashboard.

• the show is marked as active.

Schedules and Timesolts are not affected.