Support machine placement in bundle export

* Service placement on machines is based on unit placement, per deployer requirements.
* LXC, though partially implemented, is not officially supported because deployer support is spotty.
LXC is the only (sort of) supported container type by deployer. So for KVMs we'll create colocation info (e.g. grab that mysql and wordpress live on it) but we won't create a special deployer name for it.