Date issue with using beginning of collection week

[geneorama]

Once again, I've encountered an issue with the dates not showing up in WindyGrid.

My "fix" in #47 uses the first day of the collection week as the main date. This solves the problem dates appearing in the future (if a collection is entered midweek, the end of the week hasn't happened yet), but it creates a new issue that the dates are artificially stale and roll off too soon. So, if we collect on Wednesday, enter data on Friday, then by next Tuesday the "date" is no longer "in the past week" so it falls off the display for collections "in the past week".

Based on conversations with @tomschenkjr I think the best solution is to have two dates

1. A date for the "week", which could be the beginning of the week.
2. A date for the actual collection time, which would be the best number to use for the mapping purposes.