If by some chance you have read this blog in the past you may notice the order of some articles has changed. Basically instead of grouping subjects in "techniques" I have moved to the use of labels instead. I think this will make it much easier to access information on specific topics. However to do this meant cutting and pasting bits of older articles into new ones hence the huge number of apparently new posts today. Apart from this post all the others with today's date are just old posts reorganised, I hope for the better.