Option to export in the app

[nbalint]

It would be helpful to be able to automatically and at regular intervals export the pump data that the Uploader receives from the pump. A set of different csv files (like boluses.csv, basal.csv etc) would be great - ideally, each gzipped (csv.gz) and saved to a folder on the Android device that is accessible to other apps.

This would make it possible to use the Uploader with other systems in addition to nightscout.