Linked density preview to penwidth

polargraphcontroller 2.3.0

• Added: Density preview is now posterized by default, and is linked to the
  pen width setting. So should be able to use this to better visualise the link
  between pen width and grid size.
• Fixed: Queue preview bug: http://www.polargraph.co.uk/forum/polargraphs-group2/code-software-forum2/updated-controller-thread504.0/#postid-2938
  thanks jbscribble.
• Fixed: Slight improvement in pixel rendering speed.

Also forgot I did the release version numbering wrong last time. Back to datestamps.