Shade time series data where individual qc bits are tripped

[cgodine]

Currently, there is functionality to add shading in plots to data points where QC is tripped (#207). This works for displaying where any QC bit is tripped, but having the ability to show where a specific QC bit is tripped and being able to display the corresponding flag_meanings attribute description in the legend would be helpful in visualizing some of the results of the machine learning being implemented by the DQ Office.