[web] allow configuration of the Content-disposition value The `set_content_type` function now takes and optional `disposition` parameter to control the value of this HTTP header. Use of `Content-disposition: inline` with a filename parameter are valid, so the presence of filename does not allows to choose between `attachment` and `inline`

if repo.system_source.dbdriver == 'postgres':
    sql('ALTER TABLE appears ADD COLUMN weight float')
    sql('UPDATE appears SET weight=1.0 ')