SLATE_TEXT_ATTRIBUTE was the macro that allowed the FString -> FText pass-through support, and was deprecated in 4.8 in favour of using SLATE_ATTRIBUTE with an FText type. This is being removed for 4.10 and SlateFileDialogs was still relying on the deprecated behaviour.
This change removes its reliance on SLATE_TEXT_ATTRIBUTE, and also cleans up a load of SLATE_ATTRIBUTE parameters should have been using SLATE_ARGUMENT instead.
#codereview Dmitry.Rekman
[CL 2628829 by Jamie Dale in Main branch]
- Uses separate style and not Core.
- A new button to create the directory.
#codereview Nick.Atamas, Matthew.Lewis, Josh.Adams
[CL 2592945 by Dmitry Rekman in Main branch]
