Version Control With Subversion Source

* ch04.xml (Repository Layout): don't even mention the idea of laying
out a repository indexed by branch. Make a xref to cmpilato's stuff
about 'project roots'.

(Best Practices): split into 2 sections about manual merge-tracking
and using --dry-run to preview merges.

(Working with your branch): make a quick forward xref to 'svn
switch' section.

* ch07.xml (servers): document all the ssl- variables in 'servers' file.

(miscellany): add missing varlistentry tag to autoprops
section. Document "log-encoding' and 'use-commit-times' variables.