Integrates the concept map generation  with the book creation process:
- The preprocessor gets terms relationships information from the Glossary.rst
file.
- After the book is generated, the postprocessor parses the glossary.html file
to retrieve term definition in HTML format, and save the graph definition JSON
file inside html/_static directory.
- Modifies conceptMap.js to read the new JSON graph definition file instead of the
old XML file.
- Updates the documentation accordingly.