TurnKey Linux Image Factory - Master Appliance

The master appliance is based on the core appliance, buildbot 0.8.6p1
and Debian wheezy.

The master factory appliance runs a buildbot master process in an EC2
cloud and uses instances of outscale-factory-slave appliances to build
TurnkeyLinux appliances.

Caveats:
 * The EC2 auth credentials needs to be filled in manually in
   /var/lib/buildbot/.boto
 * A lot of settings are hardcoded.
[WIP] Add buildmaster_utils module

Utility functions used by the Buildbot master config.
Add appliance_buildsteps module

The module encapsulates the EC2 calls that are used to drive the build
process on the master side.  This is in fact just a wrapper over the
create_ami module from the outscale-image-factory tools.

Note that Buildbot still manages the slaves instances itself. See
master.cfg and the EC2LatentBuildSlave class.
Import outscale-image-factory tools in a git submodule