Begin changing API calls to Augur

There is still much left to do, because Augur's (undocumented) login system does not appear fit for task. A number of temporary changes exist in this branch, such as the user's hardcoded name "John".

Here's what's definitely missing:

• Logging into Augur
  • This is partially implemented, but the /user/authorize and /user/session/generate endpoints in Augur both fail
• Saving browser session for persistent login
• Automatic session refresh
  • This was implemented before I got here, but whatever it's trying to do, Augur disagrees
• Marking groups as favorites
  • Implemented, but not confirmed working. Checking the JSON response would be good, but I see no value in that while the logins just don't work (and they are necessary for favorites)
• Creating new repo groups for the user
  • (see above)
• Adding new repos to the current group
  • (see above)

As an aside, there are times when it looks like React state jank is being used to track repo group names. It looks that way because that's exactly what's happening. Augur likes to look up repo groups by their names (which I note is not uniquely-identifying information) as opposed to integer IDs (which are).

Style changes (i.e. anything within a 10-mile radius of CSS) are not found on this branch. See the figma, new-project-styling, and explore-styling branches for that progress. The changes there are incompatible with the changes here, but show more or less how things should look. Mockups will have to be redesigned to fit the Augur face/off surgery.