[pkg] various fixes
- add missing files to MANIFEST
- exclude doc/changes from dh_installchangelogs (it's a directory, which
dh_installchangelogs doesn't expect)
- fix doc build in debian package
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