Version Control With Subversion Source

Remove description of now-absent wiki/ top-level directory.

Remove versioned Google wiki pages.

[de] Added forgotten sections to svnadmin freeze command.

* Sync with English version.

* Fixed build failure reason.
* Completed sync with English version.

[de] Synced reference chapters with English version.

* en/book/ref-svnadmin.xml
In the `svnadmin` command line reference, mentioned that `svnadmin load` now
accepts `--revision` option.
- http://subversion.apache.org/docs/release-notes/1.8.html#svnadmin-load
- http://subversion.tigris.org/issues/show_bug.cgi?id=3734

Patch by: pavel.lyalyakin{_AT_}visualsvn.com

* en/book/ref-svnadmin.xml
Add `svnadmin freeze` subcommand to `svnadmin` command line reference.
- http://subversion.apache.org/docs/release-notes/1.8.html#svnadmin-freeze
- http://svn.apache.org/viewvc?view=revision&revision=1376228

Patch by: pavel.lyalyakin{_AT_}visualsvn.com

* en/book/ch06-server-configuration.xml
Document mod_dav_svn's 1.8 keyword expansion feature.

Patch by: Pavel Lyalyakin <pavel.lyalyakin{__AT__}visualsvn.com>
(Tweaked by me.)

* en/book/ref-svn.xml
Fix a weird rendering issue that causes option descriptions to break
across lines.

Patch by: Pavel Lyalyakin <pavel.lyalyakin{__AT__}visualsvn.com>
(Tweaked by me.)