Specify approach for resource meta-data

We need to specify the approach for meta-data associated with a given resource (document or container), understanding that there is already a variety of metadata to account for today, and a need to be able to support new forms of metadata in a standardized way over time.

Examples of meta-data include (but are not limited to) wac permissions, shape validations, and audit history. Meta-data should apply to both RDF and non-RDF resources. Meta-data should be fully portable. Meta-data should be tied to the lifecycle of the resource. Meta-data should have a coherent mechanism for authorized access.

There are several issues that are directly or tangentially related to this, including #63, #65, #58. Creating this one issue as an overarching place to track them across the board.