Processes section working examples

[chriswyatt1]

Still many of the examples do not work, which is fine for hypothetical, but would be cooler if they actually process data too. E.g. Blast run Section:6.4.

[chriswyatt1]

Add exercise. Where we write a working blast example, show that running this will fail. But by finding a correct container on Dockerhub, we can add this to the nextflow.config and get a basic example to run.