EntityDescriptor and EntitiesDescriptor

[Ghostbird]

How do I get EntiesDescriptor in the metadata?

// Summary:
// The EntitiesDescriptor element contains the metadata for an optionally named
// group of SAML entities.
public class EntityDescriptor

The documentation is plural, but the element is singular. It seems that EntitiesDescriptor XML element is not supported, and the documentation is wrong.

[Ghostbird]

I looked into this a bit more, and there's some weird stuff that seems to belong on Saml2Metadata that's implemented on EntityDescriptor. It seems centred around the ctor that takes a Saml2Configuration and signMetadata option.

The function EntityDescriptor.ToXmlDocument(); is exclusively called from Saml2Medata.

[Ghostbird]

I've got a local branch almost working. I hope to make a PR next week.

[Ghostbird]

See #187