Validator Extension Enhancements

[dslik]

The following enhancements have been requested for the CDMI validator extension:

1. Allow a validator to mark an object that passes (or fails) validation with specific metadata (or rels, e.g. a "validated_by" pointing to the schema in the version of the validator used to validate, with annotation of when, etc). Currently the validation extension only permits marking with the validator path and the validation result.
2. Allow a validation specification to be attached to a container so that it is "sticky" with the container. Currently the validation extension requires creating a seperate data object that defines the validation. (both embedded schemas, and pointing to a schema object/URI)
3. Add clarity around long-running validations and how this interacts with the object's completionStatus

It also would be useful to add an example showing how to use $ref to use external schemas not explicitly stored in the validation object. Having these "schema objects" is a useful pattern and we should provide guidance and examples. This may be best as a seperate "schema extension".