[$20] - View Scorecards & Complete Appeals buttons at the Challenge Details page

[birdofpreyru]

Recently we have added View Scorecards and Complete Appeals buttons to the challenge listing in the Dashboard (#992, not yet in production).

The goal of this ticket is to add such buttons to the challenge details page (hosted in https://github.com/appirio-tech/tc-site repo).

Here is how the header of the challenge details page looks right now after the registration:

Once submission phase is over both buttons become gray and inactive.

Now, we should check (1) if the logged in user has submitted to the challenge; and (2) the appels phase is active. If both are true, we should hide the inactive unregister and submit buttons and show View Scorecards and Complete Appeals buttons instread. For now, let's do it only at the devlopment challenge page. The View Scorecards button should be green, the Complete Appeals one should be red (the same colors / styling as the unregister/submit buttons, the links should be the same as used for these buttons in the Dashboard).

Once appeals phase is over, it is ok to keep showing inactive uregister/submit buttons for now.