Homemade graph display

!1337 (merged) 😎

Closes #1064 (closed)

• Full feature parity with the graphs that we previously had.
• elkjs is designed to layout large graphs asynchronously, so it can work using a Service Worker. We don't care about that at all (and it won't use a service worker by default), but it still requires web-worker without even specifying it in its package.json. We therefore depend on web-worker just to make Webpack happy, but we don't actually use any of it.
• Graph edges are a separate component, but nodes remain inside the graph because a large amount of node components caused a lot of flickering and some performance issues.
• The graphs displayed in the process configuration page and the template preview were exact duplicates and have been merged into a Graph/WorkerRuns.vue component.
• The full cleanup of the old nodes computed properties, still used by WorkerRunWithParents, WorkerTag, and the configurations list and form, will be done as a followup in #1070 (closed), and will be impacted by the DataImport→Process rename.