[schema2sql] properly consider skip_relations parameters.
This is the same bug as yams #286912. Also, introducing a unique function
telling if the relation should have a table or not unhide some other problems
related to computed relation, or missing skipped relations information.
# -*- coding: utf-8 -*-
# copyright %(year)s %(author)s, all rights reserved.
# contact %(author-web-site)s -- mailto:%(author-email)s
#
%(long-license)s
"""%(distname)s precreate script, executed at instance creation time or when
the cube is added to an existing instance, before the schema is serialized.
This is typically to create groups referenced by the cube'schema.
"""