Referenced here: #118

Right now the Puck.js BLE library times out after ~30s to try and avoid getting completely locked up if a device is printing non-stop.

Right now apps that need data downloaded do this: https://github.com/espruino/BangleApps/blob/master/apps/gpsrec/interface.html#L112

And we should abstract that away so it's not copy/pasted all over the place, and then I guess the sane solution might be to just read data in 100kB chunks using multiple Puck.write calls.

Either that or the Puck.js lib could just be extended to allow the timeout to be skipped.