Ansible playbooks to migrate OONI data-pipeline

Includes the playbooks needed to migrate OONI data-pipeline containers and
configuration to a remote server.
Reference: trac-13825
> Why is the default_release set to testing?
The 'default_release' corresponds for the -t for apt and we use it to install the 'docker.io' package from the testing repo.

> What if the target debian machine is stable?
This is why we have used APT pinning priorities

>  Also I believe you also need to install a > 3.8 series kernel.
I'm not sure if we can install a different kernel version on the VM, this can happen most probably with KVM depending on the configuration. Note that on current server data-pipeline docker runs on a < 3.8 kernel.

> Docker should probably not be installed from the debian package, but using the get-docker script
I would prefer to install docker.io as a package rather than installing it from a script this way we can upgrade docker easier.