GATK: add docker files

src/docker_modules/GATK/4.0.8.1/Dockerfile

+FROM broadinstitute/gatk:4.0.8.1
+MAINTAINER Laurent Modolo
+
+ENV GATK_VERSION=4.0.8.1
+
+RUN cp gatk /usr/bin/

src/docker_modules/GATK/4.0.8.1/docker_init.sh

+#!/bin/sh
+docker build src/docker_modules/GATK/4.0.8.1 -t 'gatk:4.0.8.1'