* Fixed FileUploadWidget deserialize function so that preview_data is added to tmpstore implementations that return a copy rather than the actual data.
* Updated deform.js, removeSequenceItem function to select the $before_node element more specifically (previous implementation may break when there was a sub sequence)
* Updated setting of preview_url so that the tmpstore data isn't set twice, rather just the original data object and the tmpstore get object are set.