Version Control With Subversion Source

(Network Model): Rework to be ... Pilatoan, and revert the changes
to the section IDs made when moving this section from the Server
Configuration chapter. (It was rather the point of using such IDs
to allow us to move sections around without breaking URLs in our
HTML forms of the book.)

* src/en/book/ch-server-configuration.xml
* src/en/book/ch-customizing-svn.xml
Update cross-reference IDs.