[config] turn internal configuration methods building appobjects search path into normal method rather than class method as this is useless and make path filters difficult to override (we had to override the class attribute, as instance attributes were not seen). Also rename related methods for consistency with current vocabulary

doc/book usr/share/doc/cubicweb-documentation
doc/html usr/share/doc/cubicweb-documentation
debian/cubicweb-doc usr/share/doc-base/cubicweb-doc