LoTW export and upload

In regards to magicbug/Cloudlog#127 

I've built in functionality to export an ADIF file of log entries that have not been sent to LoTW. During the export, entries are marked as being sent.

Users need to sign and ADIF file using tQSL.

The user then selects the signed .tq8 file, and uploads.

Cloudlog will then take the file, log in to LoTW, and push the uploaded file to LoTW for processing.