Add Parameter Set

[vdice]

Porter implemented Parameter Sets, a correlate for parameters to the Credential Set originally defined in the cnab-spec repo and its golang implementation existing here in this repo. This issue is therefore around migrating the re-usable Parameter Set definition(s) and methods into this library for the broader community to use.

• [ ] Migrate Parameter Set definition and methods into this repo. See https://github.com/deislabs/porter/blob/main/pkg/parameters/parameterset.go and other applicable logic (like storage) in https://github.com/deislabs/porter/tree/main/pkg/parameters

• [ ] Add a SchemaVersion field to the imported Parameter Set struct like was done for Credential Sets in https://github.com/cnabio/cnab-go/pull/229 so implementations can pin to a known version of a Parameter Set definition. This will necessitate adding a section to the cnab-spec repo similar to https://github.com/cnabio/cnab-spec/blob/master/802-credential-sets.md and/or the addition in the same repo of a json schema definition.

[carolynvs]

It seems to me that unless we change the schema for credentialsets to be generic, there will need to be two schema: one for each. So parameters' schemaVersion would be cnab-parametersets-1.0.0-DRAFT-* and credentials would be cnab-credentialsets-1.0.0-DRAFT-*.

I'm not sure consolidating them together and causing the breaking change for such little value is worth it.

[vdice]

I started on this but realized we'd want to get https://github.com/cnabio/cnab-go/pull/229 in first. (Porter currently references code from the branch in 229, including some of the files intended for porting over to this library.)

[carolynvs]

Closing since we've since changed direction about putting non-runtime concerns into cnab-go.