Docker Container: Init 1 & Initialisation

- Now using a setup script before starting the app. The separation of
the run script and the setup script will make service initialisation a
little bit clearer
- Now calling start.sh script as ENTRYPOINT and S6 as CMD. This way
when running the container with just a shell script, the start.sh
script will be launched before, making debugging easier
- Added note about `.dockerignore` ignored during Docker Hub Automated
Build

docker/s6/openssh/setup

@@ -0,0 +1,12 @@
+#!/bin/sh
+
+if ! test -d /data/ssh; then
+    mkdir -p /data/ssh
+    ssh-keygen -q -f /data/ssh/ssh_host_key -N '' -t rsa1
+    ssh-keygen -q -f /data/ssh/ssh_host_rsa_key -N '' -t rsa
+    ssh-keygen -q -f /data/ssh/ssh_host_dsa_key -N '' -t dsa
+    ssh-keygen -q -f /data/ssh/ssh_host_ecdsa_key -N '' -t ecdsa
+    ssh-keygen -q -f /data/ssh/ssh_host_ed25519_key -N '' -t ed25519
+    chown -R root:root /data/ssh/*
+    chmod 600 /data/ssh/*
+fi