Order coordinates by longitude, latitude

Ordering by a "latitude|longitude" string works but is not optimal, obviously. I think it's better to
* ... order by the decimal numbers instead of the string. This should be obvious.
* ... order by longitude first instead of latitude. This fits a little bit better to the shapes of the continents and the projections we are usually using. Coordinates will appear grouped: North America, South America, Europe/Africa, Asia. I think this is better than South-North.