Create usa.poly

This poly is meant to be used for address maps
Create russian-federation.poly

Polygon for address maps. It could use more detail at the borders with China, Mongolia, Kazakhstan and some more of these countries. But there is so much unmapped white space there that it doesn't contain addresses anyway.
Create Readme_polygons.txt

Some explanation about the polygons in this map
Update Readme_polygons.txt
Merge pull request #51 from hvdwolf/master

Addition of USA and Russian_federation polygons for address map generation