add docker files for samtools:1.7

src/nf_modules/SAMtools/1.7/Dockerfile

+FROM ubuntu:18.04
+MAINTAINER Laurent Modolo
+
+ENV SAMTOOLS_VERSION=1.7
+ENV PACKAGES samtools=${SAMTOOLS_VERSION}*
+
+RUN apt-get update && \
+    apt-get install -y --no-install-recommends ${PACKAGES} && \
+    apt-get clean

src/nf_modules/SAMtools/1.7/docker_init.sh

+#!/bin/sh
+docker build src/nf_modules/SAMtools/1.7 -t 'samtools:1.7'