Use stable identifiers for 0.5 embedded badgeclass and issuer when possible.

[ottonomy]

In 0.5 assertions, the badgeclass and issuer record are embedded in the assertion. This is also possible with 2.0 assertions, except with 2.0, it is required that the issuer supply an identifier id value for these embedded objects. To make up for the lack of that identifier in 0.5, the validator synthesizes a _:<UUID> blank node identifier. This changes every run of validation of the assertion. Since this data is returned as part of the final result, it would be nice if the blank node identifier assignment could produce a regular value for multiple runs of validation of the same assertion.

An example regularized identifier might be _:<assertionId>:badge indicating that it is the badge property in the assertion object (and extending this to _:<assertionId>:badge:issuer for the issuer in the badge in the assertion.)

It may also be wise to investigate whether the _: scheme is appropriate. Maybe there is another choice that would be better for machine-assigned IDs.