Makefile: add rules for docker image build

Dockerfile

@@ -0,0 +1,16 @@
+FROM alpine:3.6
+
+ENV DATA_DIRECTORY /data
+ENV PASSWORD_FILE /data/.htpasswd
+
+RUN apk add --no-cache --update apache2-utils
+
+COPY rest-server docker/*_user /usr/bin/
+
+VOLUME /data
+
+EXPOSE 80
+
+COPY docker/entrypoint.sh /entrypoint.sh
+
+CMD [ "/entrypoint.sh" ]