plugin attach, XEP-0363: progress id can now be specified:

progress id can be specified in options, using the "progress_id" option, this can be
more handy for frontends to keep track of attachments progresses.

sat/plugins/plugin_misc_upload.py

@@ -111,6 +111,8 @@ class UploadPlugin(object):
         @param options(dict): option to use for the upload, may be:
             - ignore_tls_errors(bool): True to ignore SSL/TLS certificate verification
                 used only if HTTPS transport is needed
+            - progress_id(str): id to use for progression
+                if not specified, one will be generated
         @param profile: %(doc_profile)s
         @return (tuple[unicode,D(unicode)]): progress_id and a Deferred which fire
             download URL when upload is finished