Polygon objects should represent an area on Earth surface and support covering the area with an uniformly-spaced grid.
Issues to be fixed:
* common.geo should use only one Geod object for all the geodetic transformations.
* Point.get_equally_spaced_points() calculates azimuth to target point only once and uses it to sequentially create intermediate points. That results in final point being off by latitude if source and/or destination points are not on equator.
* common.geo is not fully test-covered.
* Line object self-intersection check can fail with both false negative and false positive results if line crosses the international date line.
* Line and polygon objects should check that their points are spread no further than 180 degrees by longitude.
