Add ImageCanvas

[quajak]

Cosmos currently has no way to draw/edit images (bitmaps for now) which have been loaded, beside direct manipulation of the array in bitmaps.

I think the best way to fix this would be to add a VirtualCanvas implementation of Canvas, which takes a Bitmap and implements the necessary methods to allow the use of the various drawing methods on it. Methods such as Display would throw NotSupportedException.

We could further also add a method to export a Canvas to an Image.

[ghost]

There's an easy way to do this. Split the image into pixels and draw the pixels one by one.

[terminal-cs]

i might try to work on this sometime later, it should be quite easy