Fixes #1971: Gageplots - fix Print appearance, Fixes #1976: Add note about toggling data series

[maggiejaenicke]

Closes #1971

• Adjusts printer CSS
• Adds forced page breaks between plots in the HTML

• Fixes issue of ALL flood stats showing up when page printed, now it should just be the selected ones

  Closes #1976

• Adds note about toggling data series to each plot

[maggiejaenicke]

Should be fixed! It was just adding the month + 1 as a string for some reason instead of an int. Good catch--most plots have instantaneous values so the url uses a date from two weeks ago instead of the current date, which is why most plots are fine. It was likely just erroring for any plots that don't have IV.

[amedenblik]

Deployed to https://dev.streamstats.usgs.gov/gageplots/