Fix up/down keys in multi line cell editors

Don't propagate up/down key strokes to the table, because the table
would call event.preventDefault() in its own "stop propagation
interceptor" and the cursor would not move in multi line string fields.

Change-Id: I4b8db89aae8da120e239f92a45cfa06f457bf7b1
Reviewed-on: https://git.eclipse.org/r/c/scout/org.eclipse.scout.rt/+/173857
Tested-by: Scout Bot <scout-bot@eclipse.org>
Reviewed-by: Beat Schwarzentrub <bsh@bsiag.com>

org.eclipse.scout.rt.ui.html/src/main/js/scout/table/editor/CellEditorPopup.js

@@ -41,6 +41,15 @@ scout.CellEditorPopup.prototype._initKeyStrokeContext = function() {
     new scout.CellEditorCompleteEditKeyStroke(this),
     new scout.CellEditorTabKeyStroke(this)
   ]);
+
+  // Don't propagate up/down key strokes to the table, because the table
+  // would call event.preventDefault() in its own "stop propagation
+  // interceptor" and the cursor would not move in multi line string fields.
+  this.keyStrokeContext.registerStopPropagationInterceptor(function(event) {
+    if (scout.isOneOf(event.which, scout.keys.UP, scout.keys.DOWN)) {
+      event.stopPropagation();
+    }
+  });
 };
 
 /**