[doc] get back baseviews documentation into the code, enhance it and reorganize the module accordingly
also properly deprecates SecondaryView as it should have been done a while ago.
Document: cubicweb-doc
Title: CubicWeb documentation
Author: Logilab
Abstract: Some base documentation for CubicWeb users and developpers
Section: Apps/Programming
Format: HTML
Index: /usr/share/doc/cubicweb-documentation/index.html
Files: /usr/share/doc/cubicweb-documentation/*.html