Edit a created Challenge

[Sch3lp]

Why this feature
I just created a Challenge, but after pressing Submit, I noticed there was typo and now there's no way of fixing it. I cannot even delete the Challenge, so it'll just take up space when selecting challenges for a Competition...

Tasks

• Make a Challenge clickable from the Challenges Overview, should navigate to challenge/123/edit
• New REST API Endpoint to update a Challenges name, points, etc.
• Integration Test that creates a challenge, creates a competition using it, and then modifies the challenge. The Competition using the challenge should not be effected (challenge at coupling time should not be effected)