Delays compared to previous period

[devinmatte]

On the delays page, it would be great to know if delays are an improvement or have gotten worse both overall and for any category by checking the last period (up to a reasonable limit)

As in if we're looking at the last year (52 weeks) we should also in the background query the previous 52 weeks to show comparisons +/- (similar to what we do on the shutdown tracker)