Add a dockerfile so that LibertyOS can be built from a docker image. This will allow LIbertyOS to be built in a "container" so that all dependencies, etc will be built in the docker container and will not contaminate the host operating system. I will try to create a sample Dockerfile and post it here when I am done. I'm a beginner in dockerfiles, so maybe someone with more experience in docker can take a look at the file I post and suggest improvements.