Add "sum" to basicstats aggregator

[puckpuck]

Feature Request

Proposal:

Add sum metric to basicstats.

Current behavior:

sum is not a computed aggregate.

Desired behavior:

sum would be part of computed aggregates in conjunction with count, min, etc.

Use case:

Although this can be computed (mean * count) it would be easier and consistent with many other metrics platforms if this was delivered out of the box. I would be happy to do this myself as a PR, but wanted to see if there was any reason why it wasn't done initially.

[danielnelson]

I think it is probably something we can do, so long as we also do #3413. I imagine there will be interest in other simple aggregations.

@toni-moreno Do you have any thoughts on this?

[danielnelson]

Implemented in #3797 and will be in 1.6, thanks @cpacey