Add ability to download data from Online portal item

[kerryrobinson]

To make it easier for users to get the demo data, especially on mobile platforms, let's add an option to download data (instead of sideloading it). It could work similary to the download options we already have in our samples app.

Requirements:

• New tool (download icon) to download the data from a public portal item
• Portal item is a well-known item for the DSA demo data (stretch goal- allow the user to configure that to a different portal item)
• Data is unzipped into the DSA data folder

Definition of Done:

• Design discussed and agreed
• Implementation done
• Tested and verified