Color palette selection

[lukasolson]

This isn't quite finished yet, just because I'm not really happy with the user experience (and it also changes the current experience, which is probably not ideal), but the majority of the work is done.

This PR adds the ability to choose custom colors on visualizations. To pick a new color for a visualization, just click on the corresponding label in the legend, which brings up a list of colors to choose from. Clicking on one of the colors updates the visualization, and if you save the visualization, these changes are persisted.

I don't like the current user experience for a couple of reasons: first of all, because clicking on the legend used to filter by the corresponding value (which is now commented out) and second, because it's just kinda hokey and could use some more polish. (Paging @alt74...)

--EDIT--

Rashid made a bunch of changes to this and now the UI is totally functional and ready to be reviewed.

Closes #1362.

[tomryanx]

Just a thought: instead of breaking the current behaviour when clicking the legend, add a color wheel logo thing which changes the behaviour of legend clicks. Or have the color wheel bring up the full legend in color selection mode.

Anyway - thanks a lot for bringing us closer to a feature that will be much appreciated!

[rashidkpc]

Have a branch working off this, filter buttons still need some work, but the behavior will be that clicking on the legend item brings up the legend item details where you can choose a new color or choose to filter the series in/out. The old behavior only allowed for filtering "in".

There is on small gotcha with this system and that is that the colors are mapped to the label, which means if the label changes at all, the color changes. For example, if you change the field formatter for say a numeric field, colors are going to reset. There's no nice way around that right now as the label is used as the series ID. We need to, not in this pull, divorce the view from the model.

[rashidkpc]

Pull to your branch here @lukasolson lukasolson#8

[rashidkpc]

Test should pass with lukasolson#8

[rashidkpc]

[lukasolson]

When you add multiple metrics, then switch to percentage mode, the colors all change (because the labels have changed). I don't know if this is scoped to this initial issue or not, but it's a funky behavior.

[rashidkpc]

As noted in the pull to @lukasolson's branch, the above issue is out of scope for this pull. I think we're good functionally here now. Need one more set of eyes on the code

[rashidkpc]

We're basically good here. @panda01 noticed an issue when starting up, but we don't think its related to this pull. Once @panda01 gives the LGTM we're good to merge.

[panda01]

This LGTM!