Allow for refresh = False / 0 etc. to turn off refresh

Change-Id: I6b2a55598153f6e52d7809582aed94ee1d67cec1
diff --git a/config/config.py b/config/config.py
index 4bd4963..67d3bfa 100644
--- a/config/config.py
+++ b/config/config.py
@@ -223,7 +223,10 @@
                 try:
                     self.visualisation.refresh = config.get(section, 'refresh')
                     if self.visualisation.refresh is not None:
-                        self.visualisation.refresh = int(self.visualisation.refresh)
+                        if not is_positive(self.visualisation.refresh):
+                            self.visualisation.refresh = None
+                        else:
+                            self.visualisation.refresh = int(self.visualisation.refresh)
                 except ConfigParser.NoOptionError:
                     pass
                 except: