standardize repo addition and install

root/etc/cont-init.d/94-r-src

@@ -0,0 +1,12 @@
+#!/usr/bin/with-contenv bash
+
+echo "**** Adding r repo ****"
+if ! dpkg -l | grep gnupg > /dev/null; then
+    apt-get update && apt-get install -y gnupg
+fi
+
+if [ ! -f "/etc/apt/sources.list.d/r.list" ]; then
+    curl -s https://cloud.r-project.org/bin/linux/ubuntu/marutter_pubkey.asc | apt-key add -
+    source /etc/lsb-release
+    echo "deb https://cloud.r-project.org/bin/linux/ubuntu ${DISTRIB_CODENAME}-cran40/" > /etc/apt/sources.list.d/r.list
+fi