sample data added for docbook-tutorial
rename build file from buildhtml.xml to build.xml and render to xhml4 instead of xhml5
re-organize books structure
re-organize books structure
Revert "re-organize books structure"

This reverts commit 695ff2feb3ccb3aa5120fb6de4ca773c0ee5376d.
Merge branch 'feature/docbook-tutorial' of https://github.com/yquan/docbooks into feature/docbook-tutorial
include popular image format during build
content contribute
refine sample to make it w3c validated