Add gui plugin

[tmptrash]

It should visualize all the data in a world
Add stuff:

• Zoom by mouse scroll button
• Move into 4 directions (by mouse or arrow keys)
• in add_listeners() func x, y should be calculated according to the size and offset of the canvas, because canvas may show only a part of big world (zoom, scroll). For now we just put a pixel with x,y.
  Update: https://github.com/Rust-SDL2/rust-sdl2/blob/master/examples/gfx-demo.rs