Improve screen real estate utilization in legends

[jccq]

Kibana 4.4 introduction of color selection seems to have had quite an impact on real estate utilization and the result could use optimizations example

Kibana 4.2

Kibana 4.4 (plenty of wasted space by default )

frankly also the gray line might seem confusing/less appealing (ugly/hacky dares one to say? :) ).
I wonder if a cleaner version is possible, with better visual real estate utilization out of the box.

Proposal: an option in the widgets about "use end user color configurable legend" vs "plain old legend" note that "old style leged". Note, the only needed addition to the old legeld would be the ability to click and pt a (positive) filter.

[timroes]

Duplicate of #13813. I know this one is older, but the other one had more discussion in it.