Support Solar Midnight

Add a feature to query Solar Midnight, similar to Solar Noon.

This is a little bit more tricky for obvious reasons... that it, it may fall in the AM or PM??? If so, perhaps offer both solar midnights before and after the solar noon in an arrary.

I found the solar midnight term used here: http://www.geoffr524.com/NOAA_Solar_Calculations_May_2011/NOAA_Solar_Calculations_May_2011.htm

Robert