Add a title, description, and license to the ontology header

[hoodcm]

Part of #5.

Check	Data checked	Why
missing_ontology_title	Ontology header	Tools show the title.
missing_ontology_description	Ontology header	Tools show what the ontology is for.
missing_ontology_license	Ontology header	Users can see the license in the file.

The header now reads:

• Title: RadLex radiology lexicon
• Description: The RSNA RadLex® radiology ontology, a set of terms for use in reporting, decision support, data mining, data registries, education, and research.
• License: RadLex License Agreement and Terms of Use

The description matches the README wording in #12. All tests pass.

[jclerman]

Although it's implied by the word "radiology" in the first clause, I suggest being explicit about the type of reporting RadLex is intended to support. Less ambiguous for a general audience.

Suggested change

	<dcterms:description xml:lang="en">The RSNA RadLex® radiology ontology, a set of terms for use in reporting, decision support, data mining, data registries, education, and research.</dcterms:description>
	<dcterms:description xml:lang="en">The RSNA RadLex® radiology ontology, a set of terms for use in radiology reporting, decision support, data mining, data registries, education, and research.</dcterms:description>

[jclerman]

for consistency with the description and to distinguish between what we have, and a flat lexicon, I suggest:

Suggested change

	<dcterms:title xml:lang="en">RadLex radiology lexicon</dcterms:title>
	<dcterms:title xml:lang="en">RadLex radiology ontology</dcterms:title>