Additional fields on ticket templates

Ticket templates can now carry additional fields of your own, for the details your team always needs but WannaTrack didn't ask for.

• Add fields per ticket type from the template builder, for example a commit ID on bugs or an environment on incidents.
• Make them mandatory. Mark a field as required and a ticket of that type can't be created without it.
• Right where you need them. The fields appear on the create form and on the ticket itself.