backport stable branch

fix pb with bytes field processing: currently when an existing file is edited and no new file is specified, it finds no value in req.form and so try to detach the current file, which is wrong. In that case, nothing should be done. So introduce a new UnmodifiedField exception that may be raised in field's process_form_value method (catched in field.process_posted).

fix NameError

don't call handle_inlined_relation where we're not on the relation'subject

don't add another _cw_edited_field hidden when build_context is called twice (may occurs with inlined relation forms)

cleanup

don't use matching_groups() for is_in_group implementation

a few french translation typo corrections

rename need_navigation into paginable paginable has been recently introduced by changeset d4eeaf0393e2. We already had the need_navigation attribute to control the same thing (pagination). As paginable sounds like a better name, deprecates need_navigation (bw compat ok). Also: * fix main pagination functions responsability * deprecate limit_rset_using_nav in favor of paginate/do_paginate * navigation module should be renamed to pagination at some point

backport tracker permission utility functions into the cw.schemas package