Support more than 256 bins

[DJMcNab]

Currently, if we try and perform a render with more than 256 bins (e.g. a render larger than 4096 by 4096 pixels), we stop rendering below the 256th bin.
I believe that this limit only occurs in binning, as all the algorithms assume there are fewer bins than the workgroup size of that element.

This was debugged following the trail from #548 (comment).
I don't really understand how this issue is occurring in that case, as even full screen on a retina 5k Mac screen, there should still be only 240 bins being rendered. Additionally, the video demonstrating this has in-congruent behaviour with this theory, as the "Try the tutorial" button is still appearing. This suggests that user is experiencing a different issue.