[sql] preprocess_entity uses lgdb helper's SQL converters. The preprocess_entity does not yield anymore the conversion logic for different base types, but relies on a new SQL_CONVERTERS dictionary of the db helper. This will allow later inclusion of new base types.

# -*- 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 schema"""