Extra oVirt ebuilds and dependencies

This PR adds four new ebuilds:

app-emulation/ovirt-engine-cli
app-emulation/ovirt-engine-sdk
app-emulation/ovirt-iso-uploader
dev-python/kitchen

I also added metadata/layout.conf that enables thin-manifest and update-changelog, to make usage of repoman more convenient and follow the Gentoo developer guidelines.

See http://wiki.gentoo.org/wiki/Repository_format/package/Manifest#Thin_Manifest and http://www.gossamer-threads.com/lists/gentoo/dev/241423?do=post_view_threaded for more info on the subject.