Add option for rotating copies of pole polygons when using poly_area

[ngs333]

This feature is related to work done for resolving issue #44 .
As issue 44 indicates, the function poly_area yields discontinuities of the area calculated for polygons near the pole.
Also as work for that issue indicates, one can improve on the area calculated for the pole polygons by function poly_area
so that area values are no longer discontinuous and in fact are almost the same as what would be calculated using the GCA (great circle area algorithm) (Note that GCA cannot necessarily be applied to all exchange grid cells, thus the existance of poly_area function). This is done by (merely) making a copy of the polar polygon, rotating it away from the pole to some other earth surface location, and calculating the area of the rotated polygon. Although the work for issue 44 is not complete, NCTools apps should have the feature of a user specified option to rotate copies of polar polygons for the purpose of calculating the area via function poly_area.

[ngs333]

The work for this was done and merge in PR 209.