release VS in docker

[ChristinaXu2017]

This pull request will change the way to install Variant spark:

1. install Hail through pip install hail==0.2.74

• our scala package of variant spark is not required hail dependency, eg run examples/command-line/local_run-importance-ch22.sh without Hail installed
• the package au.csiro.aehrc.third.hail-is was the copy of Hail=0.2.74, according to dev/misc-deploy-hail-to-maven.sh
• the only scala class: src/main/scala/au/csiro/variantspark/hail/methods/RFModel.scala requires Hail, which is only called through python code: "import varspark.hail as vshl; vshl.init() ..."
• pip install hail==0.2.74 will install /usr/local/lib/python3.7/dist-packages/hail/; and add to java path during vshl.init()

2. install variant spark through pip install variant-spark
3. create a Dockerfile where jdk8, python3.7, spark-3.1.2-bin-hadoop3.2, hail==0.2.74 and pyspark==3.1.2 will be installed.

??? trouble shooting: RUN wget -q https://archive.apache.org/dist/spark/spark-3.1.2/spark-3.1.2-bin-hadoop3.2.tgz it is so slow. on 28Oct, I tried wget in my local pc, it took nearly one hour to download it ( 218M). Maybe the archive.apach.org was too busy at that time.