Last week, Azure Data Factory (ADF) team upgraded the way JSON is used in ADF. The main reason for this upgrade is to simplify or clarify ADF artifacts that are linked services, datasets and pipelines. This upgrade enhance the clarity of the JSON used in these artifacts. Here the link to ADF release notes to get all JSON format changes.
https://azure.microsoft.com/en-us/documentation/articles/data-factory-release-notes/
Christian