erp5_configurator: add erp5_graph_editor to installed BT list
The ability to create graphs of workflows, which existed by default with the old DCWorkflow, has been moved to the erp5_graph_editor, which is not installed by default.
This MR aims at allowing graph by default by installing this BT with the configurator. The initial purpose of this change was to make the ERP5 developer tutorial usable immediately after configuration, without needing to install any extra BT.