Added a couple of console test for Message's references. Updated Message client return type to MessageEnvelope.
Moved common ConsoleTest classes to a shared project. Reviewed GroupClient.
Reviewed Invitation client.
Moved Invitation client default configuration to a separate partial class. Minor variable rename for Message client.
Updated Notification client to return expected type.
Updated Notification client to accept Relation array as parameter.
Renamed Relationship to RelationshipEnvelope. Added Page DTO for Search client results.
Added GetByTopicId in Message client.
Refactored JsonServiceClient common properties into a shared project.
Added .NET 4.0 and .NET 4.5 project shims. Rearranged solution's project folders back into `src` and `tests`.