Renamed kpi to is_kpi

Created by: stefanoborini

Boolean flag on the OutputSlotInfo renamed to is_kpi

force_bdss/core/output_slot_info.py

@@ -16,4 +16,4 @@ class OutputSlotInfo(HasStrictTraits):
 
     #: True if the value associated to this output slot must be exported as
     #: a KPI.
-    kpi = Bool(False)
+    is_kpi = Bool(False)