Add Dockerfile for the Django app

I added the Dockerfile for the future Django application. It's based on
the rails Dockerfile with the following tweaks:

- Installation of Python 3 and pip
- Edit of the Python symbolic link to force the use of Python 3 by
default

I decided to store the app in the same folder as the rails app was as
they are not meant to work side by side. It will also facilitate the
debugging for developpers who were working on the rails app. If they
need to look into it for debbugging reasons, the path where to find it
is still the same.

Signed-off-by: Matthieu Berjon <matthieu.berjon@inria.fr>

django/Dockerfile

+FROM allgo/base-debian
+
+# install system packages + bower
+RUN apt-getq install mariadb-client libmariadb-client-lgpl-dev-compat	\
+	redis-server curl imagemagick git ca-certificates		\
+	gcc g++ make libc6-dev file libffi-dev libgdbm-dev libgmp-dev	\
+	libncurses5-dev libncursesw5-dev libreadline6-dev libssl-dev	\
+	libyaml-dev openssl procps systemtap-sdt-dev zlib1g-dev		\
+	nodejs npm supervisor nginx-light zip				\
+  python3 python3-pip \
+	&& ln -s /usr/bin/nodejs /usr/local/bin/node			\
+	&& npm install -g bower
+
+# Ensure python 3 is the default version
+RUN rm -f /usr/bin/python && ln -s /usr/bin/python /usr/bin/python3
+
+# install allgo sources + run setup script
+COPY	. /opt/allgo
+# RUN	pip install -r requirements.txt
+
+USER	allgo
+WORKDIR /opt/allgo
+# CMD	["run-allgo"]
+LABEL   dk.migrate_always=1