1. Output different-colored edges for parent-child resource
relationships
2. Allow the changing of edge colors via command-line parameters
3. Allow the skipping of the parent-child graph or the
dependency graph when calculating all edges
This modifies the Graph interface slightly to allow an edge to specify
what color should be used when drawing it.
This commit does two things:
1. All dependencies of a resource, both implicit and explicit, are
communicated directly to the engine when registering a resource. The
engine keeps track of these dependencies and ultimately serializes
them out to the checkpoint file upon successful deployment.
2. Once a successful deployment is done, the new `pulumi stack
graph` command reads the checkpoint file and outputs the dependency
information within in the DOT format.
Keeping track of dependency information within the checkpoint file is
desirable for a number of reasons, most notably delete-before-create,
where we want to delete resources before we have created their
replacement when performing an update.
