Version Control With Subversion Source

`svn diff` in Subversion 1.8 accepts `--ignore-properties` option.
- http://svn.apache.org/r1239553
- http://subversion.apache.org/docs/release-notes/1.8.html#svn-diff
* en/book/ref-svn.xml
(svn.ref.svn.sw.ignore_properties): New option `--ignore-properties`
for `svn diff`.

Follow-up to https://sourceforge.net/p/svnbook/source/5006/

Updated the description of the mod_dav_svn keyword expansion feature
with a paragraph taken from the patch by Andreas Stieger:
https://sourceforge.net/p/svnbook/tickets/193/

Minor fix (removed extra newline).

New `--compatible-version` option for `svnadmin create` that replaces
`--pre-X.Y-compatible` options (they are deprecated in Subversion 1.8)
- http://svn.apache.org/r1407279
* en/book/ref-svnadmin.xml
Added `--compatible-version` option and mentioned that
`--pre-X.Y-compatible` has been deprecated in Subversion 1.8.

`svnadmin hotcopy` supports `--incremental` mode starting from Subversion 1.8.
- http://subversion.apache.org/docs/release-notes/1.8.html#incremental-hotcopy
- http://subversion.tigris.org/issues/show_bug.cgi?id=3815
* en/book/ref-svnadmin.xml
Add `--incremental` option to `svnadmin hotcopy` command-line reference.
* en/book/ch05-repository-admin.xml
Mentioned that `svnadmin hotcopy` now supports working incrementally.

Update Japanese site index file.

* www/index.ja.html
Update to track latest English version. Also, replace broken links
to Japanese translation with ones that work.

Patch by: jtdan <officejtdan{__AT__}gmail.com>

* Updated links.
* Added old version index page.

[de] Synced original English message.

Update English website references with new SourceForge URLs.

Patch up some svn:externals definitions.