In the Location Recorder decide what to do with saved failed locations

[Frizlab]

Currently, we save an array of failed location, with the failure error (the saveFailedLocations variable). But these are saved in memory only!
We should decide what to do with them.

One option would be to do nothing.
Another would be to let the user retrieve the locations whose save failed in a csv file (or whatever). This would require a UI to alert him some locations failed to be saved.

Ideally we’d need to have some analytics to know if there actually are locations that failed to be saved. There is a high probability that none will fail to save.