US-23 Adding published and updated date information to exhibitions

User story

Can be implemented with #167 (closed)

As a visitor, I want exhibitions to display published and updated date information so that I can understand how recent or relevant the information is. EDIT: included under this issue are also updated logic for exhibition cards.

Prerequisites

• Exhibitions page exists.

Acceptance criteria

• Exhibitions details contain published and/or updated at fields.

Sprint Ready Checklist

1. Acceptance criteria defined
2. Team understands acceptance criteria
3. Team has defined solution / steps to satisfy acceptance criteria
4. Acceptance criteria is verifiable / testable
5. External / 3rd Party dependencies identified