demote repeated add warnings to trace level because there are so many

1. repeated adds are usually due repeated series of nodes on OSM ways
2. edges currently use semantic rather than identity equality, so this
does not distinguish GB errors from genuine double edges in input
3. edge lists may eventually be replaced with CopyOnWriteArraySet<E>

opentripplanner-routing/src/main/java/org/opentripplanner/routing/graph/AbstractVertex.java

@@ -120,7 +120,7 @@ public int hashCode() {
     @Override
     public void addOutgoing(Edge ee) {
         if (outgoing.contains(ee)) {
-            LOG.error("repeatedly added edge {} to vertex {}", ee, this);
+            LOG.trace("repeatedly added edge {} to vertex {}", ee, this);
         }
         outgoing.add(ee);
     }
@@ -142,7 +142,7 @@ public synchronized void addOutgoingConcurrent(Edge ee) { // create TemporaryEdg
     public void removeOutgoing(Edge ee) {
         outgoing.remove(ee);
         if (outgoing.contains(ee)) {
-            LOG.error("edge {} still in edgelist of {} after removed. there must have been multiple copies.");
+            LOG.trace("edge {} still in edgelist of {} after removed. there must have been multiple copies.");
         }
     }
 
@@ -162,7 +162,7 @@ public Collection<Edge> getOutgoing() {
     @Override
     public void addIncoming(Edge ee) {
         if (incoming.contains(ee)) {
-            LOG.error("repeatedly added edge {} to vertex {}", ee, this);
+            LOG.trace("repeatedly added edge {} to vertex {}", ee, this);
         } 
         incoming.add(ee);
     }
@@ -178,7 +178,7 @@ public synchronized void addIncomingConcurrent(Edge ee) {
     public void removeIncoming(Edge ee) {
         incoming.remove(ee);
         if (incoming.contains(ee)) {
-            LOG.error("edge {} still in edgelist of {} after removed. there must have been multiple copies.");
+            LOG.trace("edge {} still in edgelist of {} after removed. there must have been multiple copies.");
         }
     }