Profiles

This is just the first part of the profiles cleanup, one step before things get really ugly. Every single change here is non-functional and should have no impact on any builds. The only almost-significant change is the gdbm use flag changed from unset to set by default but that was compensated for by adding package.use lines for the two packages that this impacted to keep the old behavior.

These changes start to consolidate all CoreOS specific profiles into a new 'coreos' directory.

For reference a diff of the sdk and amd64-generic profiles: https://gist.github.com/marineam/6557621/revisions

Depends on https://github.com/coreos/portage-stable/pull/47