Version Control With Subversion Source

Book tweaks.

* doc/book/TODO: remove finished stuff
* doc/book/TODO: fix typo.

Fix a not-quite-truth regarding 'svnadmin setlog'.

And yet still more Subversion book work.

* doc/book/TODO:
Remove svndumpfilter TODO.

* doc/book/book/ch05.xml
(svndumpfilter): (Mostly) Document this badboy.
(Migrating a Repository): Explain the --parent-dir option for svnadmin load.

* doc/book/book/ch04.xml
(Undoing Changes): Add a reference to the new svndumpfilter documentation.

Begin documentation of svndumpfilter.

Still more Subversion book work.

* doc/book/TODO:
Updating TODOs, updating TODOs...

* doc/book/book/ch05.xml
Fix a bogus reference to 'svnadmin list-used-dblogs' (thanks, Juanma
Barranquero, for noticing). Also, talk about some limitations of
Berkeley DB.

* doc/book/book/ch07.xml
Note how 'svn status' and 'svn commit' work with respect to
svn:externals.

At least sort the lettered status codes alphabetically.

More Subversion book work.

* doc/book/TODO:
Trade one TODO for another.

* doc/book/book/ch05.xml
Update the Repository Layout section.

More Subversion book work. This time, we take on Chapter 5!

* doc/book/TODO:
Remove the relevant TODOs.

* doc/book/book/ch05.xml
Rework some parts of this chapter. Add a new "Berkeley DB" section
under "Repository Basics", add a placeholder for "svndumpfilter"
documentation, and do a bunch of other juggling around of stuffs.

* doc/book/book/ch09.xml
Tracking a moving xref across the plains of Rohan.

Fixup the documentation about restoring default configuration values.

* doc/book/book/ch07.xml
(Configuration Area Layout): Make the appropriate edits.

* doc/book/TODO:
Remove the relevant TODO.

Reorganize and expand chapter 4 a bit. ("Branching and Merging")

* ch04.xml: make the need for "manual merge tracking" clearer and more
explicit. create a new "use cases" section for merging which
demonstrates (a) repeated merging of one branch to another, (b)
undoing a change, (c) resurrecting deleted things.

* ch06.xml: implement a rewording suggestion from Blair.

* REVIEW: remove the suggestion.