Produce a clear and concise documentation for each Dockerfile

[davidonlaptop]

All Dockerfile should be documented using a README on GitHub and on the Docker Hub front page (ideally, this should be the same file).

Good examples include Docker's Jenkins or MySQL images.

At the minimum, we should have these infos (taking Adam as an example):

• What is Adam ?
• What is Docker and what is a Docker image ?
• Dependencies (*)
• How to use this image? (**)

(*) The dependencies include Docker, and the Base Docker Image. When we used different branches (src vs released version), we should also document which branch uses which base docker image.
(**) In the case of Snap, Adam, Avocado, we should put a small example which downloads (wget) a chromosome from 1000 Genome project's ftp and run each tool.

[flangelier]

Snap done

[flangelier]

adam done

[flangelier]

spark done

[flangelier]

scala done

[flangelier]

Java done

Remaining:
Avocado
Hadoop

[flangelier]

Hadoop done

Remaining:
Avocado

[flangelier]

Done for avocado!!!