Implement persistent handles for pages

[kaylaondracek]

Description:

As a user, I need to be able to reference and/or cite a page I found on the fishrappr application by a persistent handle.

See lower left of screenshot:

Acceptance Criteria:

• On image viewer page, user should see a space where they can copy a persistent page handle
• User should not be able to edit the text within this space (this is something Colin found during accessibility review on current implementation)
• The handle should be unique per page