Summary: Ref T3583. Adds edges, query relationships, etc. Lots of debugging/temporary UI. My general intent here is to use edges to track where panels appear, and then put additional data on the dashboard itself to control layout, positioning, etc. Dashboards don't actually render yet so this is still pretty boring. Test Plan: {F149175} {F149176} {F149177} Reviewers: chad, btrahan Reviewed By: btrahan Subscribers: epriestley Maniphest Tasks: T3583 Differential Revision: https://secure.phabricator.com/D8916