Basic check for homedir permissions

Several guides suggest using data directories under your homedir,
rather than the default /opt area.  This is fine, but on RHEL6 and
similar distros homedirs are very restrictive 0700 permissions which
doesn't allow things like httpd to pass through to serve up files.

Even though stack.sh is taking over the host, changing permissions
automatically is not a nice idea.  So we just warn when it looks like
this is happening.

Change-Id: I9cd70e7fe90638a2a5c3b8fd94756afacac7c7be
xenapi - cleanup

Add error on unitialised variable to the scripts. This way some issues
were identified. Also modify README with fresh variables. The patch
includes:
 - Add SWIFT_HASH to the README
 - Add XENAPI_CONNECTION_URL to the README
 - Add VNCSERVER_PROXYCLIENT_ADDRESS to the README
 - Introduce UBUNTU_INST_IFACE which is the OpenStack VM interface used
   for the netinstall. It defaults to eth3. Previously this parameter
   was set by the combination of HOST_IP_IFACE and the undocumented
   NETINSTALL_IP
 - get rid of NETINSTALL_IP
 - xenrc includes CLEAN_TEMPLATES
 - xenrc no longer tries to change directory
 - remove chrooting from prepare_guest.sh (STAGING_DIR was always / )
 - remove DO_TGZ variable from prepare_guest.sh
 - use arguments to call prepare_guest.sh, instead of env vars
 - Fix backslash escaping in prepare_guest_template.sh

NOTE: networking is about to be addressed in a separate change.

Related to blueprint xenapi-devstack-cleanup

Change-Id: Ie9a75321c7f41cc9a0cc051398d1e6ec2c88adfa
Merge "Basic check for homedir permissions"
Basic cells support

Adds support for running a region and child cell within a single
devstack environment.

README.md has been updated with some info on getting started.

Rebased/updated from initial work by Andrew Laski <andrew.laski@rackspace.com>.

Change-Id: Ic181da2180ccaa51df7efc9d66f7ccb820aac19b
Merge "xenapi - cleanup"