Source code checked in, #49a14915dcab

Removing serialization from Code First CSDL code path. - Adds ctor to EdmItemCollection allowing construction from a passed EdmModel instance. - Adds CSpace validation to EdmModel. Added missing validation rule: EdmNavigationProperty_BadNavigationPropertyBadFromRoleType - Some fixes to how Code First builds the conceptual model (errors were previously masked by serialization). - Store SGP in MetadataProperties on conceptual side. - Reworked ModelNamespaceConvention to be a model-level config convention. This is required because GlobalItem namespaces should be immutable in core metadata because they are used as part of item identity.