[urlpublish] RESTPathEvaluator now use vid_from_rset This avoid cases where vid may be unexpectedly overwritten. For instance when you define a custom vid for a mime type in VID_BY_MIMETYPE, it will currently be overriden by the URL publisher when you access to /<etype> with the proper Accept header. To do so, a new 'check_table' argument is introduced, which may cause bw compatibility problems if the function has been monkey-patched. Also pep8 a bit the tests. Closes #5705835

[server/sources] use decode_extid in datafeed

[server/sources] add decode_extid method avoids having the same dance in both eid_type_source variants