Add a Level System

[reteps]

Add a level system to Pwny CTF.

• Add tables to CTFd to store levels (or calculate everything client-side)
• Show a level progress bar after challenge is completed, indicating your progress towards the next level.
• Create cool animation when a challenge is completed. I was thinking that on a correct submission, there is an "explosion" effect that creates mini pwny-logos depending on how many points the challenge was, and then those are sucked back into the level bar.
• Potentially show each user level in a leaderboard-esque page (Option to disable / enable the scoreboard?)
• Potentially show users level top right of navbar
• Potentially show users level on profile page
• Potentially show users level on challenge page