Update app download page description with new Android data location and process

[JamesMBallard]

Per #369 (comment), https://www.arcgis.com/home/item.html?id=82ce2d85e21c4326bc072d441b636e5e needs to be updated with the next app push with the latest changes to pick up the new app location.

Additionally, we need to update the steps to deploy the data to the device, as they have changed. From our testing, it seems like you now need to access this data path (/data/data/com.esri.arcgisruntime.opensourceapps.DSA_Handheld_Qt) via Android Studio's device explorer (accessed in Android Studio > View > Tool Windows > Device File Explorer. I think we should add a short blurb explaining this in the readme and the AGOL item

cc @dtedder