expose "interval" property of EventGenerator

dream/simulation/GUI/Batches.py

@@ -39,7 +39,7 @@ class Simulation(DefaultSimulation):
       "_class": "Dream.EventGenerator",
       "name": "Attainment",
       "property_list": [schema['start'], schema['stop'], schema['duration'],
-                        schema['method'], schema['argumentDict']]
+          schema['interval'], schema['method'], schema['argumentDict']]
       }
     conf["Dream-Configuration"]["gui"]["exit_stat"] = 1
     conf["Dream-Configuration"]["gui"]["debug_json"] = 1

dream/simulation/GUI/Default.py

@@ -135,6 +135,12 @@ schema = {
     "_class": "Dream.Property",
     "_default": "-1"
   },
+  "interval": {
+    "id": "interval",
+    "type": "string",
+    "_class": "Dream.Property",
+    "_default": "10"
+  },
   "duration": {
     "id": "duration",
     "type": "string",