Migrate V5 Challenge API to Community App

[Oanh-and-only-Oanh]

Begin work on April 1, 2020
API copilots- @ThomasKranitsas and @callmekatootie
Front end copilot- @LieutenantRoger
Branch:
https://github.com/topcoder-platform/community-app/tree/feature-challenge-v5

https://github.com/topcoder-platform/topcoder-react-lib/tree/feature-challenge-v5

V5 Challenge API migration should help with resolving the following Challenge issues:

1. MM Leaderboard: Past challenges scores are not visible #3392
2. Past Challenges (MMs) are returning empty #4112
3. Sub community filters are not working #3278
4. Some challenges are not shown when revisiting the Challenge Listing page from Challenge details page #3122
5. [$80] Stats for CODE track not getting computed/displayed #3571
6. [$40] Fix the display of the reliability % on profiles #3394