Query on _tag Criterium.
Required new Hl7.Fhir.Api  & Hl7.Fhir.Model dll's.
Querying on _profile and _security criteria.
MongoSearcher reports UsedParameters again in the SearchResults, plus (new) a list of errors.
Added tests for that.
Criterium.ToFilter now evaluates generic parameters first, then the metadata criteria (was the other way round).
Merge branch 'develop' of https://github.com/furore-fhir/spark into develop

Conflicts:
	Spark.Search/MongoSearcher.cs
Fixed Tag Search and tests on Tags.
New Hl7.Fhir.Api dll's, with the Query.Count fix.