Start milestone 3

- Add functionality to query online sources (Keyservers, etc) for
  certificates.
- Use introducers to determine which UserIDs should be fetched from
  online soources. Check certifications before importing certifiactes
  into the local cert store.
- start docker image for local end-to-end testing.

docker/mta_provision/usr/bin/test.sh

@@ -0,0 +1,17 @@
+#!/usr/bin/bash
+
+TEST_DIR=$1
+
+if [ "$TEST_DIR" == "" ] ; then
+  echo "USAGE: $0 DIRECTORY_WITH_TESTS"
+  exit 1
+fi
+
+for TEST in $TEST_DIR/* ; do
+  if bash $TEST ; then
+    echo "$TEST: success"
+  else
+    echo "$TEST: failure"
+    exit 1
+  fi
+done