Improve Warehouse save()

[totalhack]

Currently a Warehouse can only be safely saved if it was created with reference to a config file and the Warehouse config was not changed in memory after init (if so it would be out of sync with the referenced file). This works OK in use cases where a config file is the master structure of the Warehouse and you aren't editing a Warehouse in memory, but it would be better if the Warehouse could reconstruct and save the current active config back to a specified file path in save() even if it wasn't created from a config file/url.

One caveat is if the Warehouse was created from a remote config file there may be no way to post changes back, so it would only be able to save a local file config without additional changes to try to support pushing warehouse changes to other locations (remote files, git, s3, etc).

One way or another this process should be cleaned up. Either the door needs to be closed on in-memory editing of a Warehouse config (a file is the only possible master and all changes go through that) or we need to support reconstructing and saving a config from the current Warehouse settings.