feat(coreos-base/oem): add the initial oem partition support

this (great looking) code adds the oem partition and supporting scripts
and services. AMI is the first target use case.
fix(sys-apps/kexec-tools) provide ebuild for binary version of kexec
fix(coreos-base/coreos): Drop criu from images for now.

Hitting a weird compile error, will sort out another time.
Merge pull request #95 from marineam/criu

fix(coreos-base/coreos): Drop criu from images for now.
fix(sys-apps/kexec-tools) fix Manifest to handle kexec binary properly
Merge pull request #94 from gregkh/kexec

fix(sys-apps/kexec-tools) provide ebuild for binary version of kexec
Delete oem.service
Merge pull request #83 from polvi/add-oem

feat(coreos-base/oem): add the initial oem partition support