Upgrade DocTools version to 31
Upgrade DocTools version to 31

* Add one more level to section menus.
* Add "hidden" and "expanded" options to section menus.
* New styling of abstracts using a panel.
* Upgrade CodeMirror to 5.6.0.

HuangLS/neo4j,HuangLS/neo4j,HuangLS/neo4j,HuangLS/neo4j,HuangLS/neo4j