Restructure module exports, import SCDL CRUD API objects + tests...

... I'm not nearly satisfied with this packaging of SCDL because SCDL is inherently a set of concepts and patterns that apply to a data model but are not exactly a data model. A future revision of this module will convert the expression of SCDL from an onm data model declaration and associated CRUD API, to a SCDL-derived onm data model factory based on the recently-published onmd-daenerys module.