Changes for 3.0.8

• LinkingBaseTool.isValidCycle, when using a TreeModel, now correctly assumes that Diagram.validCycle is either CycleMode.DestinationTree or CycleMode.SourceTree, depending on the value of Diagram.isTreePathToChildren.
• Fixed toggling the Diagram.grid visibility - which would in some cases fail to update the grid.
• Fixed confusion with InputEvents when calling CommandHandler.showContextMenu during a GraphObject.click or Diagram.click event.