renamed osg::Image::pixelFormat(), internalTextureFormat(),dataType() to
osg::Image::getPixelFormat() etc. These changes are to bring it more
into line with the style of the rest of the OSG.
Updated the rest of the distribution to take account for these names changes.
osg::Drawable. Added osg::Image::readPixels to osg::Image.
Made osg::LightSource to default to cullActive set to false to that LightSource
nodes don't get culled by default.