top wspr transmitter rankings using total km/Watt

I added a new 7-day km/Watt transmitter rankings list to the top of the km/Watt pages.

On 17m, DL6NL has the highest total (almost 3 times as much as the next highest station).

The rankings are based on the last 7 days of wspr reports and add all the km/Watt values of the unique reporters hearing the transmitting station each day.

A minimum of 7 reports (average of 1 per day) is needed to be on the list. This helps to keep the lists somewhat clear of bad decode data.

Hopefully these lists will show the lowest power that can reach the maximum number of reporters for each band.