Checklist: Add a Function for Admins to configure templates for checklists *must have*

[DeniseMaterna]

As Admin I would like to be able to create, configure, activate and edit any number of templates for checklists:

• If a checklist item is changed, there should be a check mark "Apply changes to existing checklists".
• Before saving the template, a preview with the changes highlighted should be displayed.
• Elements: checklists (tabs) / category / checklist item
• Idea: use markup if necessary
• There should be manual, time-based and action-based checklist items
• For each checklist item, it should be possible to define whether an e-mail notification is sent and to which Role
• For each checklist item, it should be possible to define whether the item is linked to a event (e.g. X days before) / additionally display the actual date
• The visibility of a checklist item should be linked to a specific role (e.g. only service team, or also bookers)