[dataimport] fix db-namespace default value handling
In a fresh new instance, the "db-namespace" option is set as empty
by default in the "sources" file.
This seems correct but empty string is not a valid pg_schema and
actually means that we should use "public"
Web side development
====================
In this chapter, we will describe the core APIs for web development in
the *CubicWeb* framework.
.. toctree::
:maxdepth: 2
publisher
controllers
request
searchbar
views/index
rtags
ajax
js
css
edition/index
facets
internationalization
property
httpcaching
resource