[book] several fixes in the rst files
- prevent duplicate markup definitions,
- use existing Workflow markup instead of redefining one (in baseschema.rst)
- include dataimport
- fix non-existant directive autodocfunction
- remove the empty 'embedding.rst' file
usr/lib/PY_VERSION/*-packages/cubicweb/entities/
usr/lib/PY_VERSION/*-packages/cubicweb/ext/
usr/share/cubicweb/cubes/
usr/lib/PY_VERSION/*-packages/cubicweb/*.py