Version Control With Subversion Source

Document some options which lacked documentation:

* svnadmin's --config-dir, --deltas, --fs-type, and --wait

* svnlook's --diff-copy-from, --extensions, --full-paths, --limit,
--non-recursive, --verbose, and --xml

Also, flesh out the documentation for svn's --extensions option for
completeness and correctness.

Finally, finish the work of replacing statically listed subcommand
options with xref's to their descriptions.

* en/book/ch09-reference.xml
Document the --ignore-whitespace, --native-eol, --reverse-diff,
--strip, and --summarize options.

Clever or insane? You decide.

* en/book/ch09-reference.xml
Add id="" to all 'svn' option descriptions, and replace static text
in each subcommand's Option section with pointers to these IDs. As
an unexpected side-effect, the resulting ID mapping failures
identified a number of options that were not yet described in the
reference chapter.

* en/book/ch04-branching-and-merging.xml

(svn.branchmerge.basicmerging.mergeinfo): Add a sidebar on mergeinfo
inheritance.

(svn.branchmerge.nomergedata): Tweak 'Natural History and Implicit
Mergeinfo' sidebar to account for the fact that we already defined
'explicit mergeinfo'.

* en/book/ch04-branching-and-merging.xml

(svn.branchmerge.basicmerging.mergeinfo): Move the tip about "mergeinfo"
from here...

(svn.branchemerge.basicmerging.stayinsync): ...back to here, which is
the first place we use the term. Also use the <firstterm> tag.

Suggested by: cmpilato

* en/book/ch09-reference.xml
(svn.ref.svn.sw): Document the other forms the --change
option supports.

* en/book/ch04-branching-and-merging.xml
(svn.branchmerge.basicmerging.mergeinfo): Add a tip explaining
that "mergeinfo" is just shorthand for the svn:mergeinfo
property. We use this shorthand a bit in the book, but more
importantly it is used extensively everywhere else. Also
add "mergeinfo" to the index.

* en/book/ch04-branching-and-merging.xml
(svn.branchmerge.basicmerging.mergeinfo): Describe the new 1.7
notifications which occur when a merge updates mergeinfo to
describe a merge (as opposed to the traditional notifications
which describe the application of a diff).

Translation of "Tunneling over SSH". Closes ticket #314 (cf.
http://www.svnbook.de/ticket/314).

Trivial grammar fix.

"interactively" -> "interactive"