Tile rendering mode

[Tugcga]

Now the rendering always use progressive mode. It renders the whole image. Tile rendering mode is hidden from UI, because there are some problems with setup parameters of this mode. The renderer is crashed.

Try to understand, why it happens and implement tile rendering mode.

[Tugcga]

In 2.2 release it almost work, but I fail to implement it completely. With activated tile rendering in update_render_tile callback the tile contains pixels with some non-stable padding. If the size of the tile is 8x8 (for example), the buffer required 80 pixels (instead of 64), because it contains two additional 2 empty pixels at every row. In some cases this padding is 4 pixels. It's strange, because on the test console app nothing similar is happens.

So, the issue required more investigations.