Add tool to print max/min river gauge stages by WFO/state

[akrherz]

Requested additional tool that allows one to select the following:

Search by WFO or State: [entry]
Specify start time/date: [entry]
Specify end time/date: [entry]
Output type: [csv, pdf, html, etc...]

and get such a data listing. I suppose we could make this a text-only autoplot option, but need to boggle this some more to make it more generic perhaps.