[Imports] Importing tags for buildings

[Max Erickson]

A straightforward way to do it is to download the area as osm xml and
then process that file to add the new tags following the JOSM file
format:

https://wiki.openstreetmap.org/wiki/JOSM_file_format

You'd add tags to the appropriate ways and set action=modify for those
ways. The round.py script here modifies an existing tag instead of
adding tags, but it shows the general idea:
https://github.com/maxerickson/osm-round-austin


Max