Split specification.zip off into its own NuGet package

[ewoutkramer]

It's pretty wasteful to get the full 5Mb zip in your project when all you want to do is use the provided functionality in the Specification assembly.

[wmrutten]

Maybe we can also improve quality by re-generating all the StructureDefinition.snapshot components?

[ewoutkramer]

Actually, we might be better of removing the snapshot completely. Saves a lot of parsing - and the snapshots are regenerated in-memory anyway.

[wmrutten]

As always, it's a trade-off... ;p

[mmsmits]

Will replace specification.zip with FHIR NPM packages in the future. So this can be closed.