remove elm and narrative from Library files

[costateixeira]

for @brynrhodes to validate if this is the preferred way for tooling:

This commit changes the Library files:

• Replaces the narrative text in JSON files with: {"status": "empty", "div": "<div xmlns=\"http://www.w3.org/1999/xhtml\"></div>"}
• Replaces the narrative in XML files with: <text><status value="empty"/><div xmlns="http://www.w3.org/1999/xhtml"></div></text>
• Keeps the Library instances's text/cql content
• Removes ELM content (application/elm+json and application/elm+xml) from both formats
• Removes ELM references from HTML files