Add spinner to challenge screen if it is building

[mvexel]

When creating a challenge, it is not obvious if the challenge page will be updated when the status changes. It says 'building' but there is no indicator that suggests you will see it when the status changes to complete or failed. If this is the case, we should add a spinner to indicate that the user can wait for it if they want. This is the preferred UX.
If this is not possible, we should add a 'refresh' action so the user can manually refresh the status while they're waiting for the challenge to be built.