added a line to sql Dockerfile to install git

Dockerfile.sql

 FROM postgres:9.6.3
 LABEL maintainer="Alexander König <Alexander.Koenig@eurac.edu>"
 
+# install git
+RUN apt-get update &&\
+	apt-get -y install git
+
 # copy int db script
 RUN mkdir -p /docker-entrypoint-initdb.d
 COPY commul-customization/init-dspace-dbs.sh /docker-entrypoint-initdb.d/