Workflow Tab: Diachronic view

[krvoigt]

Describe the feature you'd like
* a chart next to each workflow item, accessible via a button
* workflow, gt-data, hardware -> item (always latest run)
* each item gets an extra chart with the history of benchmarking of this item
* the list in Quiver will be a list of benchmarking runs, no longer a list of items

Is your feature request related to a problem? Please describe.
currently it is not possible to determine to what extent further development has had an impact on quality and performance.

User story
As OCR-D developers, we want to be able to visualize to what extent the quality & performance of OCR-D has improved over the course of development so that we can make this transparent to the community and the DFG.

Additional context
Add any other context or screenshots about the feature request here.

[krvoigt]

clone of #148

[mweidling]

@krvoigt You can just alter the description of #148, then we can close this clone.