Add filter by citation on gage page

[amedenblik]

On the gage page, allow user to filter the Physical Characteristics and Streamflow Statistics by citation. This should go where the current filters are located for each group:

Similar to USGS-WiM/StreamStats#1136

[harper-wavra]

@Abigail770 If you have time this could be good issue to work on too, as you just completed this in SS.