Wrong transformation in CRS EPSG3395

Looks like there is still bug in EPSG3395 (after #1578, #1796 and wrong #358).

The problem is in transformation from linear projection coordinates to pixels. Current transformation sets different scales for X and Y coordinates, but it should be the same (major Earth radius). As a result, EPSG3395 raster tiles with EPSG3395 map projection are shifted (for example, relative to vector data).

I've added some tests for CRS classes, that check projections of edge pixels of zero zoom tile.