Google fusion tables will be deprecated at the end of 2019 - need to fix or remove /maps + links

[dlebauer]

On the home page, both the 'model i/o' and the 'crop model maps' tabs link to https://www.betydb.org/maps

But https://www.betydb.org/maps is broken.

I suspect that this is related to the latest release, which was deployed in August, at which point pageviews went to zero (except 2 in Nov 2018)

In addition, the google fusion tables API will be deprecated at the end of 2019. Unless someone wants to write a replacement application, I would remove this page, keeping only the links to the underlying .csv files with model outputs.