Tree view of histories

[nekrut]

We used to have a structure view of history. @carlfeberhard has implemented a prototype for a tree view. We should roll it out and test asap.

[yhoogstrate]

A while ago we have had a brainstorm on this idea as well. Large histories can become really complicated and a tree structure makes absolutely more sense as it perfectly represents the hierarchy. Really looking forward to this. Are there any screenshots of the prototype?

[pvanheus]

The Refinery Platform uses Avocado to visualise provenance. I haven't been able to test this in production, but it looks like it might be usefully incorporated in Galaxy.

[nsoranzo]

xref. #2450 and #5315