Fix doc build for glossary

Fix doc build for glossary

asciidoctor was throwing the error "invalid part, must have at least one
section (e.g., chapter, appendix, etc.)"; including [appendix] in front
of the include mollified it.

Also we don't need the duplicated Glossary / Glossary headings.

Signed-off-by: Dan Scott <dan@coffeecode.net>