TXDataWebDataset add a LoadAndAwait method

It would be useful to have a method added to the TXDataWebDataset that enabled the loading of a dataset and awaited until after the dataset was opened


another useful method would be ApplyUpdatesAndAwait.

These would enable more readable code especially when there are a series of datatsets that need processing but are reliant on a previous dataset, rather than have to keep jumping between AfterOpen and AfterApplyUpdates.