Add data containers to fix permission issues

data/Dockerfiles/data-container-vmail/Dockerfile

@@ -0,0 +1,10 @@
+FROM debian:jessie
+
+RUN groupadd -g 5000 vmail \
+	&& useradd -g vmail -u 5000 vmail -d /var/vmail
+
+RUN mkdir -p /var/vmail \
+  && chown -R 5000:5000 /var/vmail
+VOLUME /var/vmail
+USER vmail
+CMD ["echo", "Data container for mail"]