See PHI446. Ref T13088. Currently, there's no way to access older generations of a build unless you know the secret ?g=1 URI magic.
When a build has multiple generations, show a history table and let users click to see older run information.
This is currently very basic. It would be nice to show when each generation started, who started/restarted it, and what the build status was at the time the build was restarted. There's currently no convenient source for this information so just add a bare-bones, working version of this for now.
