Adding key/value store and updating Dockerfile

[tehtbl]

Hi,

I am using your ndscheduler for my own tasks. So, thank you for open source it! :) Because I needed some concurrent-safe way to save and retrieve job data for comparison of multiple job runs data, I implemented it. Also, I've updated the Dockerfile to fix security issues with actual version.

If you have questions and/remarks please let me know.

cheers, Thomas