New dockerfile for python library building

[javiermtorres]

A separate dockerfile for building the encoderfile library is now available. The image can be used to generate a library as follows (note that the /output directory needs to be mapped in the container):

docker build -f Dockerfile.python.bindings -t encoderfile-python-bindings .
docker run --rm -v $(pwd)/wheels:/output encoderfile-python-bindings