Any container definitions in ccl.toml can be given a `start_order` tag
(integer). It is recommended to not put a start_order unless a container
depends on another one (e.g. synapse needs postgres), in which case all
dependents and dependees should be given a `start_order`, with dependees
having a lower number than their dependents. It is guaranteed that the
dependees will be started first, although the container startup
procedure is outside of our control. Containers without a `start_order`
will have their operations applied asynchronously, but those with
a start order are started, well, in order from lowest to highest. "Stop"
operations are applied in the reverse order.
