app: switch to multi stage build

Mind you, the image is still about 240M in size. These Java
images don't really get much smaller.

src/ulo-storage-applications/Dockerfile

 FROM openjdk:11
-
+RUN apt update && apt install -y maven
+RUN git clone https://gl.kwarc.info/supervision/schaertl_andreas
+WORKDIR /schaertl_andreas/src/ulo-storage-applications/
+RUN mvn install
+
+FROM alpine:latest
+RUN apk --no-cache add openjdk11
+WORKDIR /
+COPY --from=0 /schaertl_andreas/src/ulo-storage-applications/target/uloapi-0.1-jar-with-dependencies.jar /opt/
 COPY ./target/uloapi-0.1-jar-with-dependencies.jar /opt/
-
-#
-# set the following ENV variables to configure the application
-# to work with your existing setup
-#
-
-#ENV ULO_SERVER=http://rdf:7200/
-#ENV ULO_REPOSITORY=compose
-
 EXPOSE 7400
-
 CMD ["java", "-jar", "/opt/uloapi-0.1-jar-with-dependencies.jar"]