Continue the reorganization effort, this time mostly focused around
gutting the Developer Info chapter.
* src/en/book/ch-advanced-topics.xml
(svn.advanced.props): Leave a TODO here about how to rework this section.
* src/en/book/ch-developer-info.xml
(svn.developer): Rework the chapter summary to reflect the change
(or, more accurately, the sharpening) in focus, from a chapter
vaguely about stuff that programmers of all sorts might want to
know, to specifically stuff interesting to users of Subversion's
API and bindings.
(svn.developer.usingapi.apr): Hand-wave about using memory pools now
that the svn.developer.pools section is deleted.
(svn.developer.layerlib): Tweak the opening sentences.
(svn.developer.pools, svn.developer.contrib,
svn.developer.contrib.join, svn.developer.contrib.get-code,
svn.developer.contrib.hacking, svn.developer.contrib.code-and-test,
svn.developer.contrib.submit): Removed! Not moved, *removed*.
* src/en/book/app-quickstart.xml
(svn.intro.install): Fix a now-broken reference by moving some of
the deleted svn.developer.contrib.get-code section here and
reworking it.
* src/en/book/ch-preface.xml
(svn.preface.free): Remove a now-broken reference link.
