[ENHANCEMENT] CSV export

[kuro68k]

I would like to export data so that I can analyse it on a computer, as well as backing it up.

The best solution seems to be a CSV export function. Ideally it would export all data for a card, all history items, rather than doing them individually. The CSV file would contain all available fields, as well as data from internal Metrodroid databases such as station names an latitude/longitude.

Other formats like XML and JSON are less suited to easy analysis with spreadsheet apps such as LibreOffice, Google Sheets and MS Excel. However, if they are easier to implement they are convertible.

Files could be saved in the filesystem somewhere that the user can access them for extraction to a PC, or the Android share dialogue could be opened to make it easy to e.g. email them to yourself.