bump(coreos-base/update_engine): Source path reorg.

All of the helper script services and systemd files are included in the
update_engine repository now. The pxe service now uses the more generic
'stub' name. Fix install path for dbus config. Remove useless udev rule.
feat(coreos-base/coreos-cloudinit): Create generic template.

Replace coreos-cloudinit-oem.service by a generic service template that
can be used for any path. Add rule to load cloud-configs installed by
the coreos-install utility.
bump(coreos-base/coreos-init): Update coreos-install script.
remove(dev-lang/python): This moved to portage-stable a while ago.
add(dev-lang/python-oem): create a minimal python for OEM

A number of cloud agents are written in python. Install a basic python
to /usr/share/oem/python with this ebuild.
fix(dev-lang/python-oem): cleanups and fixes for OEM python

Remove all RDEPENDS, OEM packages are installed after prod images are
pruned of the previously installed package database.

Re-enable XML and ctypes support since the required libraries happen to
be bundled with Python.

Assorted other simplifications.
fix(coreos-devel/board-packages): Build python-oem with build_packages
Merge pull request #506 from marineam/oem

Python for OEM
Merge pull request #504 from marineam/pxe

PXE and related updates
feat(app-emulation/google-daemon): initial google daemon

This installs the google_daemon to /usr/share/oem/google_daemon. The
service files are not installed but will instead be installed by the
cloud-config.yml
bump(coreos-base/oem-gce): install the google-compute agent
fix(app-emulation/google-daemon): grab a chown fix
fix(app-emulation/google-daemon): patch to use '*' for the passwd
hack(app-emulation/google-daemon): use right ip and interface
chore(app-emulation): rename google-daemon to google-compute-daemon
fix(coreos-base/oem-gce): use google-compute-daemon

The naming is inconsistent but lets settle on google-compute-daemon
feat(app-emulation/google-startup-scripts): initial commit
feat(coreos-base/oem-gce): add google-startup-scripts
feat(coreos-base/oem-gce): add the gce-add-metadata-host service

One of the requirements of GCE is setting up the metadata host. Do this.