Show snippet's creation date when viewing it

When a snippet is viewed it should show its creation date.

The snippet's creation date is showed in my snippets list but not when I see my snippet.

mentioned in merge request !781 (closed)

mentioned in merge request !1567 (closed)

mentioned in commit 857cc388

mentioned in merge request !1637 (merged)

Reassigned to @DouweM

Reassigned to @DouweM

Thank you very much, guys.

Status changed to closed by merge request !1637 (merged)

mentioned in commit 01315cfe