wof:population property, round one - Canada

[stepps00]

This PR includes population work for all admin records in Canada, as a first pass to close #240.

Records include the following:

• If the record has no existing population property, the record was given a default wof:population_rank property with a value of 0.
• If the record has an existing population property, the record was given:
  • A new src:population property that lists the source of the population figure.
  • A new wof:population property with an integer value equal to the existing population value in the record (priority of existing propertiyes in Expose wof:population property #240).
  • A new wof:population_rank property with an integer value, based on the wof:population figure.

Script used to complete this work: https://github.com/mapzen/whosonfirst-toolbox/blob/master/scripts/issue-240-wof_population.py

Follow-up PR(s) will include this work for all admin records in whosonfirst-data.

[nvkelso]

I spot checked a bunch of these, including Vancouver and LGTM.

Properties only, no PIP'ing. Over to @thisisaaronland.