retroactive trackers on project. PMT #97744

sticking with the same UI/approach as the PMT. only last week and week before last available
and only on the individual add tracker form from within a project, to subtly discourage
backdating trackers as a habit
Added some assertions to ensure accuracy of retroactive trackers
Merge pull request #200 from ccnmtl/retroactive-trackers

retroactive trackers on project. PMT #97744