Feature request: Normalize catalog view / installation across UX, CLI, and DRP

[mclamb]

Currently the UX catalog view is determined by the catalog_url param with its default value pointing to the upstream catalog. The drpcli cli does not use catalog_url but instead relies on a -c <catalog_file> flag that defaults to the upstream catalog. Finally, when version sets are applied to endpoints the only location from which content can be downloaded is the local catalog as specified by {{ ProvisionerUrl }}/files/rebar-catalog/rackn-catalog.json . The content must exist on the filestore having been previously created via drpcli plugins runaction manager buildCatalog and drpcli catalog updateLocal.

This is a request to normalize catalog views and operations across the various DRP components:

1. All catalog views should be satisfied by the catalog pointed to by catalog_url
2. Content is pulled form the catalog pointed to by catalog_url
3. In drpcli the catalog could be overridden for ad hoc uses via -c <catalog_file>
4. Version sets download content from whatever is pointed to by catalog_url. If using a local catalog is desired then catalog_url must be explicitly set to the local catalog file. Perhaps fall back to locally installed content so that custom content packs can also be referenced without having to build an entirely local catalog. Or perhaps support two catalogs, one for upstream and one for custom content.
5. Local/custom catalog creation should be simplified for most-likely use cases, e.g. users probably want whatever is specified in version sets to be in their local catalog.

For prod environments users can simply pin explicit versions and not have to worry about changes even if using the upstream catalog. If they pin to stable or tip then it is expected and correct for content to auto-update whenever an upstream stable or tip is updated if the endpoint is in apply mode.

This is a work in progress as far as what all is desired, but this is a starting point for ideas on simplification of the catalog viewing/management/building process.