Support "<invertYCoordinate>" tag in MapSources for TMS layers

[JSFrias]

Geos doesn't seem to support the "true" tag in the map sources xml file. Is this the case?

This is the conversion (possibly the opposite of what you would need):

def GoogleTile(self, tx, ty, zoom):
    "Converts TMS tile coordinates to Google Tile coordinates"
    
    # coordinate origin is moved from bottom-left to top-left corner of the extent
    return tx, (2**zoom - 1) - ty

Taken from here: http://www.maptiler.org/google-maps-coordinates-tile-bounds-projection/

[Gregor Sturm]

correct, the <invertYCoordinate> is currently not supported.

I can look into this when I have a little more time, or you can implement it yourself and file a pull request.