Add ability to view individual or averaged distributions

[derekcoffman]

Individual distribution will be:

• x: diameter (log)
• y: dNdlogDp (dSdlogDp, dVdlogDp)

can be for a single time or from an average of times

[derekcoffman]

Here's the easy part. To get an average size distribution (diam vs dNdlogDp). The example is from the jupyter notebook

flight_11_cdp.cdp_dNdlogDp.mean(dim="time").hvplot.scatter()

This will generate an average distribution for the entire flight which isn't terribly useful. The harder part will be to capture the start/stop times from the users selection and average over that time period.