models: Fix the json-ification of booleans
models: Add a new Distro.inherit attribute

This is part of issue #8
admin: Show the new inherit distro attribute

This is part of issue #8
sync: Respect the distro's inherit attribute

Fixes #8
kojibase: Handle the case where we run out of builds

When that happens, and we still need to iterate over packages, then all
remaining packages can just be ignored, as if we just hadn't found a
build for them.

Neveretheless, that shouldn't cause a traceback.
layout: We moved to Github
yumbase: Handle yum errors

We shouldn't traceback in the middle of a sync when the repository is
inaccessible.

Instead, raising the proper error will ensure that the package being
processed will just be treated as an error, and the sync will proceed.