Security Enhancements - deleting/editing content

1. The ability to manually delete ticket contents and attachments by any end user with appropriate permissions (full ticket subject/description content while retaining the other fields). 
2. The ability to set a retention schedule to automatically delete ticket contents and attachments after a certain period of time
3. The ability to automatically delete ticket contents and attachments for tickets with a specific tag

This is in relation to previous support tickets #11784367 &  #11834891.