dev: changes private ctor to protected.
docs: adds release note for changing accessibility of the constructor.
refactor: use memeber field instead of property to remove irrelevant

process.
refactor: introudces member field from local variable to improve

performance since the member is tread-safe.
dev: return visitor itself instead of throwing not-supported exception

when elements, not having accessibilities, are visited.
docs: fixes an exception message.
build: add pragma to suppress build warning.
refactor: inlines local variable to simplify.
build: sets minimum analysis rules to IdiomsUnitTest.
dev: implements GetReferencedAssemblies(type).
dev: introduces RestrictingReferenceException class.
dev: implements Assemblies property and adds guard clause to

constructor of RestrictingReferenceAssertion.
dev: implements Visit(AssemblyElement) of

RestrictingReferenceAssertion.
dev: implements Value property.
dev: adds scenario test for RestrictingReferenceAssertion.
build: adds release note for RestrictingReferenceAssertion.
refactor: rearrange namespaces

Jwc.Experiment.Idioms is split to Jwc.Experiment and
Jwc.Experiment.Idioms.
docs: improves XML doucment.
docs: adds release-note for re-arranging namespaces.
dev: introduces DirectReferenceCollectingVisitor.