new way to populate My Challenges based on team membership
fix bugs
fixing up tests
new tests
unique challenge projects only
from code review:  cache whitelist.  also fix UI (add space above each item in eval list)
new tests
add single team to list
Merge pull request #734 from jay-hodgson/SWC-1075

SWC-1075: By popular demand, bringing back the My Challenges section to the front page (but it's no longer based on evaluations, it's a loose team2challenge mapping)