Add stream ingest rate sampling about natscli

[ripienaar]

I made a little thing like this

This is kind of one size fits all, but I wonder if it would be better to instead allow for some generic uses by saing like:

$ nats s graph "State.Msgs" --rate

This would pick that specific field and draw it as a rate / second, else the absolute value. This allows you to do complex things like draw the rate of messages removed vs the "deleted" messages as some ratio or something like that.

But this would be much harder to use of course. Probably whats shown in the video is enough, there just isnt that much to graph.

What do you think @jarretlavallee and @derekcollison

[jarretlavallee]

That looks great to me. It is a much better approach than I was initially thinking. Being able to do comparisons would be very beneficial as well.

[derekcollison]

This looks really good to me..

[ripienaar]

OK give nats s graph and nats c graph a go

#1089