Adding tools to get image names from charts, pull images locally given a list, refactored tag and push.

Change-Id: I276e2b3f8093d39651f91d86245a80fb1563e0a8
diff --git a/developer/pull_images.sh b/developer/pull_images.sh
new file mode 100755
index 0000000..8cb6a61
--- /dev/null
+++ b/developer/pull_images.sh
@@ -0,0 +1,67 @@
+#!/usr/bin/env bash
+
+# Copyright 2018-present Open Networking Foundation
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may not
+# use this file except in compliance with the License.  You may obtain a copy
+# of the License at:
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+# License for the specific language governing permissions and limitations under
+# the License.
+
+# copy-ssh-keys.sh - Adds ssh keys to nodes given as parameters to the script,
+# after removing them from the ~/.ssh/known_hosts file on the local system.
+#
+# This script should be run interactively as it will prompt for input, and only
+# invoked once, so as not to add multiple copies of the SSH key to the remote
+# system.
+
+#############################################################
+#                                                           #
+#    Pull a list of images into the local Docker Registry   #
+#                                                           #
+#############################################################
+
+display_help () {
+  echo "Downloads the images specified to the local Docker Registry."
+  echo " "
+  echo "Usage: $0 [-s|--source image-list-file] [-h|--help]"
+  echo " "
+  echo "   image-list-file               A file where to read images from (if not read by default from stdin)"
+  echo " "
+  echo "Example usages:"
+  echo "   echo alpine:3.6 | bash $0" # read the list of images from stdin
+  echo "   cat images | bash $0" # read the list of images from stdin
+  echo "   bash $0 -f images" # read images from a file images
+}
+
+while :; do
+  case $1 in
+    -s|--source)
+      shift
+      if [[ -z $1 ]] || [[ $1 = -h ]]
+      then
+        display_help
+        exit 1
+      fi
+      custom_file="$1"
+      ;;
+    -h|--help)
+      display_help
+      exit 0
+      ;;
+    *) break
+  esac
+  shift
+done
+
+while IFS= read -r image;
+do
+  docker pull "${image}" > /dev/null
+  echo "${image}"
+done < "${custom_file:-/dev/stdin}"