Homestyx hydra

R1:dfd8b0225b3d

Add a UI element for reviewing older generations of Harbormaster builds

Summary:
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.
Repository: R1 hydra
Commit Date: Mar 13 2018