Enhancements to elapsed time chart in Admin Activity Tracking

[amcclain]

Our activity chart currently shows the simple daily average for the current filtered dataset. It would be really nice if:

• We had an option to exclude outliers, say dropping top/bottom 5% to produce a trimmed mean. Sometimes we have a random-ish hang that takes much longer than any others and skews the margin. This can have an especially outsized effect when there are not too many data points.
• We had an option to show the points as a scatterplot, which might help visually do the same. Points could be assigned a color based on the category/message.
• Could also consider a boxplot option.

Of all these, the first seems like it would be the easiest to implement and provide the most value.