Rename source/target into left/right

Author: gartens

org/polypheny/prism/value.proto

@@ -310,9 +310,9 @@ message ProtoEdge {
   // This list contains all labels associated with this node. Normal strings are used instead of ProtoStrings.
   repeated string labels = 4;
   // The system internal unique identifier of the node from which this edge originates.
-  string source = 5;
+  string left = 5;
   // The system internal unique identifier of the node to which this edge is incident.
-  string target = 6;
+  string right = 6;
   // The direction of this edge. Possible options are LEFT_TO_RIGHT, RIGHT_TO_LEFT or NONE.
   Direction direction = 7;
 
@@ -322,4 +322,4 @@ message ProtoEdge {
     RIGHT_TO_LEFT = 2;
     NONE = 3;
   }
-}
+}