Issue waypoint GPX export

[HellMapGoesCoding]

Basically, collect a list of locations for a GPX file that can be loaded into a map app for survey, like OsmAnd or something

[ ] Main export logic
[ ] Export filter - e.g. correlator only errors, missing, etc.
[ ] Waypoint names - full description is way too long for waypoints on phone app
[ ] Region - don't want whole country, just specified area - current map view perhaps