getselectedfeatures should use more efficient centroid processing

[jng]

The current getselectedfeatures.aspx/php/jsp uses MgGeometry.GetCentroid() to calculate the zoom location.

It turns out GetCentroid() does a full scan of the geometry's WKT.

For geometries with an absurd amount of vertices, this is a woefully inefficient method of calculating the centroid.

Since the purpose of this centroid is to be the zoom location, we don't exactly require a *precise* zoom location. Something approximate should suffice. So the centroid processing should change from this:

MgCoordinate pt = geom.Centroid.Coordinate
zoom.X = pt.X;
zoom.Y = pt.Y;

to this:

MgEnvelope env = geom.Envelope();
MgCoordinate ll = env.GetLowerLeftCoordinate();
MgCoordinate ur = env.GetUpperRightCoordinate();
zoom.X = (ur.X + ll.X) / 2;
zoom.Y = (ur.Y + ll.Y) / 2;

[jng]

Fixed in 2.2 (r5312) and trunk (r5314)