Don't re-align pck images to the first top/left pixel defined

For tiles that do not use the first column/rows (IE most of them) we
re-aligned the entire image to the first row/column actually used (IE
non-transparent). This caused the tile to be mis-aligned on the
cityscape, so no longer do that

This makes the stored tiles slightly larger, padded with more
transparent pixels, but memory is cheap these days...