Challenge Manager Updates

Types were simplified, and Tracks are now an actual API object: All Tracks and All Types can be cross-linked, so now just:

1. GET /v5/challenge-tracks?isActive=true
2. GET /v5/challenge-types?isActive=true

Create a challenge now looks like this:

{
  "typeId": "uuid",
  "trackId": "uuid",
  "status": "New",
  "timelineTemplateId": "",
  "phases": []
}

Thomas created a postman collection to show how to create all the current v5 challenge types: https://github.com/topcoder-platform/challenge-api/tree/develop/docs/test%20challenge%20creation