[ISSUE-410] Check switches on edgeType and make sure they have default cases

Simulator/Edges/Neuro/AllNeuroEdges.cpp

@@ -90,11 +90,12 @@ int AllNeuroEdges::edgSign(const edgeType type)
       case EE:
          return 1;
       case ETYPE_UNDEF:
-         // TODO error.
+         return 0;
+      default:
          return 0;
    }
-
-   return 0;
+   // TODO: exception throw.
+   return 0;   // default.
 }
 
 ///  Prints SynapsesProps data to console.

Simulator/Edges/Neuro/AllSynapsesDeviceFuncs_d.cpp

@@ -37,7 +37,7 @@ CUDA_CALLABLE int edgSign(edgeType t)
          return 1;
    }
 
-   return 0;
+   return 0;   // TODO: exception throw.
 }