Create GUI method to have widgets end up on a certain dialog tab

In a lot of dialogs in the Hop GUI we need to split up widgets over multiple tabs since there are so many options.  It would be nice if we could automatically generate the tabs from the `@GuiWidgetElement` annotations.

So perhaps we can add a `String tabName() default ""` method to the annotation.
If one or more elements for a specific parent ID have a non-default tab name, we generate tabs.  The widgets without name end could up in a "General" tab.