dataset_recorder: Record extra GPS info

[alexdewar]

As discussed with @aphilippides.

Currently there are various kinds of GPS info which are not being saved into data files, including:

• Raw GPS coords
• UTM zone
• GPS unit's error estimates (I think these are available)

[alexdewar]

So it looks like we actually are recording UTM zone and the GPS' "horizontal dilution" measures; it's just that this wasn't done in whatever version of dataset_recorder @tenxlenx used to collect the big RC car dataset.

Raw GPS coords should also be recorded but this should ideally be done in PR #263 which includes a bunch of other dataset_recorder-related changes.