Reorganising the developer guide

[Martin Desruisseaux <ma...@geomatys.com>]

Hello all

I'm reorganizing the developer guide in a way which (I hope) would be
easier to work on. Instead of editing directly the big final HTML file,
I splitted the document in smaller HTML files, one per chapter. The big
HTML file is now generated from the smaller files by a custom Java
program in the "sis-build-helper" module. So the directory structure on
https://svn.apache.org/repos/asf/sis/site/trunk/ is now:

  * "book/" contains the source HTML files (maybe we should rename
    "source/book/").
  * "content/book/" contains the final HTML file generated from the above.

In addition to assembling the source files together, "sis-build-helper"
also performs the following tasks:

  * Generate the tables of content.
  * Generate the navigation links in each chapter.
  * Manage the abbreviation titles.
  * Take care of some of the syntax coloring.

This allow us to remove many formatting code in the source HTML by
letting "source-build-helper" generates that formatting itself. The
source HTML files now focus a little bit more on the content. This
approach is very similar to "docbook", except that the source files are
plain HTML5 instead than inventing yet another markup language.

The assembled documentation is available in the "staging" site at
http://sis.staging.apache.org/book/en/developer-guide.html . There is
not yet new content; I plan to add some after the source files became
more easily editable. But one can test the links (should be a little bit
easier to navigate).

    Martin