Add a way to see summary metrics in line with chart

[tbragin]

When looking at a date histogram, it would be useful to see the total number of hits displayed (like we do in the date histogram on Discover). However, for a more general use case, it might be useful to see other metrics, such as query/request duration, last time refreshed, index name, etc..

[rashidkpc]

I'd say this applies to any visualization not just the date histogram

[vrushalpatil]

are we expecting new version soon ?

[tbragin]

Duplicate of #6279