"Free up space" feature to remove synced photos and submissions

Photos and submissions currently stay on the device until the survey is removed or app is uninstalled. We should offer the user a way to see how much space each survey occupies on the device and offer a way to remove synced data. We should also link them to the offline areas page so they can remove data they don't need there as well.

@jo-spek @andreia-ferreira @vittorino