Split and kill off the scripts repository

[jdreed]

The "scripts" repository is a pile of stuff that should be separated out. In particular, scripts/build-server should be its own thing, as should installer and installer/pxe. Victor suggests there will actually be very little left, but whatever is left will end up as debathena-build-tools or something. I suspect scripts will consist of things like check-unbuilt-packages, et al. (things that really are only small scripts useful for debathena-root or above)