This extension offers more advanced up-to starting and down-to
stopping, by declaring the dependencies of defstates explicitly. It
will only start or stop the transitive dependencies or dependents.
Using these functions, the defstates or substitute states *must*
declare a `:dependencies` field, which may be nil.
Build two graphs of state keywords, represented as maps where the
values are the dependencies or dependents of the keys. See also
Just like the core `start`, except with an `up-to-var`it only
starts the explicit transitive dependencies of that state.
Just like the core `stop`, except with a `down-to-var` it only
stops the explicit transitive dependents of that state.