[Box-Admins] More CI jobs

[Frank Shearar]

Hi,

I thought it high time to break up a mega-job
(http://build.squeak.org/job/ExternalPackages/) into (some of) its
subparts, because the mega-job takes far too long to run, and makes it
hard to understand the current state of play in the Squeak ecosystem.

A side effect of this is more disk usage. Please let me know if I need
to get more creative with my disk usage.

Thanks,

frank