Version Control With Subversion Source

* src/en/ch-server-configuration.xml:

- remove creds-caching section & update xrefs
- stop pushing mod_deflate
- mention that path-based authz is a perf hit
- make sure factorized path-based-authz section isn't mentioning
apache; keep it general.

* src/en/ch-advanced-topics.xml:

- add creds-caching section.
- rewrite intro to creds-caching section.

* src/en/ch-customizing-svn.html

- update xref