Convert website to asciidoctor, hosted in git and published via ASF's svnpubsub

Asciidoctor can be found here [1].

Some reasons for doing this:

• the source code for the website will be in git (rather than svn as currently), and so will be mirrored to github. Therefore users/contributors can fork our repo and submit pull requests on the docs/website.
• the generated content can be previewed locally; ASF's svnpubsub infrastructure is used only for publishing/hosting the site
• there are also some doubts about svnpubsub's long-term future, so we should minimize our dependence on it if possible
• the toolchain seems to exist already and is in use by at least one other ASF project - Deltaspike [2] - who have got the toolchain to work. (Wicket are also experimenting, [3])
• the generated pages are themeable either using Foundation (the default) or using Bootstrap .
• github natively understands asciidoc (.adoc) files, and are enthusiastic supporters (see this article of Scott Chacon, [4])
• there are editors for Asciidoctor, eg [5]
• longer term, it's possible that the docs could be converted into a book, eg using O'Reilly's Atlas platform [6]

Good starting points:

• the DeltaSpike pom.xml's. They seem to have two separate regions; the top-level site [7a,7b], and a "documentation" subfolder [8a,8b]
• these use the asciidoctor-maven-plugin [9] to convert the .adoc files to .html
• these use the maven-scm-publish-plugin [10] to update the SVN (do all necessary add/deletes to properly synchronize)
• there are also some useful templates (integrated with mvn site) at [11]
• theming with Bootstrap might be done using any of [12] or [13a, 13b] (latter is asciidoc not asciidoctor so might require some fiddling around with).

[1] http://asciidoctor.org/
[2] http://deltaspike.apache.org/
[3] https://github.com/dashorst/wicketguide
[4] https://medium.com/@chacon/living-the-future-of-technical-writing-2f368bd0a272
[5] https://github.com/asciidoctor/atom-asciidoc-preview
[6] https://atlas.oreilly.com/
[7a] https://github.com/apache/deltaspike/blob/master/site
[7b] https://github.com/apache/deltaspike/blob/master/site/pom.xml
[8a] https://github.com/apache/deltaspike/tree/master/documentation
[8b] https://github.com/apache/deltaspike/tree/master/documentation/pom.xml
[9] http://asciidoctor.org/docs/asciidoctor-maven-plugin/
[10] https://maven.apache.org/plugins/maven-scm-publish-plugin/
[11] https://github.com/asciidoctor/asciidoctor-maven-examples
[12] https://github.com/nerk/asciidoctor-bs-themes
[13a] https://github.com/llaville/asciidoc-bootstrap-backend
[13b] http://laurent-laville.org/asciidoc/bootstrap/