Contact model for use with SAML ContactPerson

This model will be referenced by multiple ContactPerson instances to reduce duplication. We find that contacts are often associated with multiple descriptors of types of contact.
ContactPerson model for SAML Metadata
Add Organizations model
Output simplecov reports on all spec runs
Add EntitiesDescriptor
Add EntityDescriptor model for SAML Metadata

Establish link to non optional EntitiesDescriptor 'parent'.

Enhance implementation of additional_metadata_location to be schema correct.
Associate ContactPerson with EntityDescriptor
Enhance test cases for EntityDescriptor
Correct use of SAML extensions field per schema
Add RoleDescriptor model for SAML metadata
Enhance expections to ensure DB consistency
Add 'abstract' SSODescriptor model