Metric points grouping

[jbrooksuk]

Split from #1918

1. when the data points and cut-off times don't exactly align - it lumps two data points in one period and none in the next - this pattern repeats.

2. instead of averaging, it adds. For instance, if it is metrics about latency - in milliseconds - then the sum doesn't make any sense. (FYI, I did set the "avg vs sum" parameter to "avg" - in case, you want to suggest that next.

[jbrooksuk]

@GrahamCampbell any idea how we can fix these issues?

[GrahamCampbell]

I'll think about this. :D

[ConnorVG]

You could attach aggregates to metrics? Just an idea.