[Denemo-devel] Documentation Cleanup

[Benjamin]

In the repository, the /doc directory could be cleaner.  For example,
DESIGN and DESIGN.lilypond contain overlapping information, ROADMAP
doesn't match the roadmap on the website, there are files that could be
generated instead of included (e.g. 4for2.abc), README is out of date,
all of the files are poorly formatted, and the DocBook format is
unreadable.

I propose the following changes:

- Reformat and clean up all the documentation
- Convert all the documentation to restructured text
- Move all documentation to the /doc directory
- Add a code-and-documentation-generation phase to the build.  This
  should happen before the release so it wont add dependencies.
  (i.e. The generated files should be included in the snapshots and
  releases but not in git)
- Add a document describing the overall layout of the code and suggest
  an approach to reading it.

Given approval, I am willing to try my hand at making these changes.