create sem annotation primer

[mbjones]

Need a chapter in the spec on how to properly use the new eml-semantics module annotation tag.

[mobb]

related to #314

[mobb]

Primer is getting long. Suggest pulling out some of the background bits into the FAQs, with links.

[mobb]

Received these actual Q's so far:

1. What does ‘dereferenced’ mean? (context: a URI in an annotation)
2. Explain the difference between an URI and a URL. (context: sample URIs look a lot like a URL. What makes it a URI?)
3. review in this section below (“When are ID’s required in the EML”) - context: annotations
4. An example of a controlled vocabulary with a rdfs label or skos label would be helpful here in this text about labels.
5. What is SKOS,
6. what is RDFS?
7. RDF Graph: a computer can’t parse this graph. What does the RDF look like?
8. Are there tools are available to help data managers select subjects, predicates, and objects to annotate with?

[mbjones]

The primer has been drafted. Moving to Review for final review.

[mobb]

IMO, ready for eml 2.2. additions/changes should have their own issues; please include "annotation primer" and tag with "documentation'