add comment about taskstatus plugin

Author: ideal

config/plugin.ini

@@ -2,9 +2,17 @@
 ; this json file exports the current status of tasks
 ; there are three status:
 ; 0 means initial, e.g. {"archlinux": {"status": 0, "schedule": "2013-11-25 19:00:00"}}
+; schedule means the next schedule time.
+;
 ; 1 means running, e.g. {"archlinux": {"status": 1, "date": "2013-11-30 00:00:00"}}
+; date means the begin time of this running.
+;
 ; 2 means finished, e.g.{"archlinux": {"status": 2, "message": "Sync succeed",
 ;                                      "exitcode": 0, "date": "2013-11-25 20:00:00",
 ;                                      "schedule": "2013-11-24 21:00:00"}}
+; date means the finish time of this running,
+; schedule means the next schedule time.
+;
+
 status_file = /home/mirror/status/task_status.json