Initial Cookbook Examples

[vitiral]

Some of these are taken from the rust cookbook, others are original ideas. I would just like to put my ideas here so se can work on them.

• thumbnails in parallel: I think this could be done more performantly (and somewhat simpler) using "threadpools" with channels.
• handling signals, especially ctrlc.
• calculate iso sum
• reimplement the main ergo_sync example.