Population updated and expanded

The indicator population has been updated and expanded to cover more countries and territories and a longer time span. It now covers 251 countries and territories, including all of the 192 UN member states. 205 of them have data going back to at least 1820 (and 51 goes back as far as 1600).

Furthermore, the documentation has been more systematic (the full documentation will be available in a few weeks).

NOTE: the unit has been changed from “1000 persons” to “number of persons”.

NOTE 2: some of the observations (particulary the earlier ones) is based on very rough estimates. See the (coming) documentation for details.