Make Report permanent snapshot

[sebastian-echeverria]

We want the Report to be a snapshot of a test run in time. It should not change if other artifact changes. Currently it depends on ValidatedSpec/TestResults, which in turn depends on Spec/TestSpec. If those change, the current Report data will change accordingly, which would violate having it being a snapshot.

Modify Report so that:

• It contains a standalone or permanent version of the content of NegotiationCard, TestSpec and TestResults. One way of doing this is by having the Report contain a copy of all the data in each of those artifacts. However, since Add versioning support to NegotiationCards and TestSpec #520 will be adding versioning support to NegotiationCards and TestSpecs, that means that each iteration of a NegotiationCard and TestSpec will never be lost/changed, as each change will create a new version. If this is so, it may be enough for the Report to link to the specific version of the NegotiationCard and TestSpec that was the current one when it was created/results where run. However, for TestResults, they will not be versioned since they are just intermediate results, so they will have to somehow be copied/maintained for the Report.
• A sort of versioning will be needed for Reports, by timestamp. Each time a new Report is created, it will have to be stored and clearly identified by its timestamp. However, it may be possible to modify specific fields in it (TBD).