Made services installation optional during build

You can user `ENV` directive in Dockerfile to disable the installation
for some services or change `image/buildconfig`.

The flags are :

DISABLE_SSHD
DISABLE_CRON
DISABLE_SYSLOG

image/services/sshd/enable_insecure_key

@@ -0,0 +1,30 @@
+#!/bin/bash
+set -e
+
+AUTHORIZED_KEYS=/root/.ssh/authorized_keys
+
+if [[ -e "$AUTHORIZED_KEYS" ]] && grep -q baseimage-docker-insecure-key "$AUTHORIZED_KEYS"; then
+	echo "Insecure key has already been added to $AUTHORIZED_KEYS."
+else
+	DIR=`dirname "$AUTHORIZED_KEYS"`
+	echo "Creating directory $DIR..."
+	mkdir -p "$DIR"
+	chmod 700 "$DIR"
+	chown root:root "$DIR"
+	echo "Editing $AUTHORIZED_KEYS..."
+	cat /etc/insecure_key.pub >> "$AUTHORIZED_KEYS"
+	echo "Success: insecure key has been added to $AUTHORIZED_KEYS"
+	cat <<-EOF
+
+		+------------------------------------------------------------------------------+
+		| Insecure SSH key installed                                                   |
+		|                                                                              |
+		| DO NOT expose port 22 on the Internet unless you know what you are doing!    |
+		|                                                                              |
+		| Use the private key below to connect with user root                         |
+		+------------------------------------------------------------------------------+
+
+	EOF
+	cat /etc/insecure_key
+	echo -e "\n\n"
+fi