Support latitude/longitude matching

[reidab]

I saw that #30 tried to add this, but relied too heavily on magic field names. This is a more in-depth stab at bringing nicer coordinate matching to csvdedupe. (This also includes the commit from #82, since nothing involving config files will run without it)

To achieve this, it's necessary to both transform the data we read from the CSV and to make an internal copy of the field definitions that we can bend to match what dedupe expects.

• For one field containing both latitude and longitude, the JSON config now supports both LatLong or LongLat types. They expect a field with the coordinates separated by some (any) non-numeric characters, so formats like -122.23,46.42, -122.23, 46.42, and -122.23 46.42 will all work.

  Behind the scenes, we split the field to the tuple of floats that dedupe expects. For the LongLat type, we reverse it to LatLong order and swap the internal type to LatLong.

• For latitude and longitude in separate fields, we add Latitude and Longitude convenience types. Internally, these are coalesced into a single LatLong field called __LatLong.

  One side effect of this change is that the training UI will now show this combined field instead of the original field names, but I think that's a fairly minor tradeoff.

[batesmotel34]

Accidentally left this. Please ignore.