Feature/base alps decorator

@mszenher or @chad-medi or @asmith-mdsol Please review and merge.

This PR adds initial functionality to generically represent a resource so that serializers have a common interface to generate representations for different media types. This is not complete, but I wanted to get a PR up for the semantic parts as the transition related interface will be a little more complicated and the PR is big enough.

Includes some refactoring of previous functionality including:
* Modified registry to register by resource name vs resource descriptor name:version
* Serialization namespacing under ALPS vs. Crichton
* Added base functionality to resource descriptor to specify embedded descriptors and sources for descriptor values to reference local attributes.

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