This significantly speeds up loading of the application; in an average of 3 tests, v1.6
loaded in 11.5s in the runtime on a Mac, whilst the webpacked version of the code
loaded in 5.53s.
2) Modify SubNodeCollectionControl, so that user can pass custom backgrid row.
3) Handling of visible parameter in SubNodeCollectionControl.
4) Customise title and delete message for Delete Cell.
5) Added Backgrid.Extension.Select2DepCell and moved Backgrid.Extension.StringDepCell from user management to backgrid.pgadmin.js.