timeseries plot

[spencerpease]

We should support timeseries plots the same way se support clock plots -- with a timeseriesBase() function with lots of arguments to tweak almost anything and a timeseries() function that has a few named styles that run timeseriesBase() with a specific collection of arguments.

The timeseriesBase() function should include at least the following options:

• add raw pm2.5 values as points or lines
• add nowcast values as points or lines
• add vertical grid lines
• add horizontal grid lines
• add shaded night coloring
• add horizontal colored AQI lines
• add side stacked bar of AQI colors
• add legend
• add title

Most of the above will probably be determined by arguments. But there should also be a section of timeseriesBase() where various things like gridLineSize and gridLineColor are set. We will hardcode these values for now and only promote them to function arguments if we need to to support requested styles.

Again, the clockPlot() and clockPlotBase() functions provide an example of how to construct these two functions.