Constituent jobs table needs an arrow of time

[copumpkin]

If I look at https://hydra.nixos.org/job/nixos/release-17.03/tested#tabs-constituents, the numbers along the top are now far too long and too similar to one another for me to be able to tell at a glance whether the latest is on the left or the right. An arrow or other marker indicating which side of the table contains the latest build would make it a lot easier on the eyes.

I say this as someone who's been looking at these tables for a while, and I still regularly forget which side is which and need to rescan the numbers.