Add kubectl get-style resource parsing to conduit stat CLI command

[rmars]

The queries proposed in #627 require more sophisticated parsing than the stat summary endpoints currently do. (Current implementation in #671 just takes a singular resource and name).

Add parsing to the CLI to take queries such as the following and generate a series of StatSummaryRequests.

  # Stat all replication controllers and services together.
  conduit stat rc,services

  # Stat one or more resources by their type and names.
  conduit stat rc/web service/frontend pods/web-pod-13je7

[klingerf]

As part of this change, we should also enable kubectl-style resource parsing for the --to* and --from* flags.

For example, as it's currently implemented, if you wanted to query all of the namespaces that send traffic to the "foo" deployment in the default namespace, you'd use:

conduit stat ns --to foo --to-resource deployment --to-namespace default

But we should make the --to flag resource-aware, such that you can instead run:

conduit stat ns --to deploy/foo --to-namespace default

And we should remove the --to-resource and --from-resource flags altogether.

[siggy]

Moving this into 0.5.0 milestone. This task is mostly complete. What remains is handling comma-separated lists of resource strings.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed in 14 days if no further activity occurs. Thank you for your contributions.