Add dpkg/rpm building capability:

* docker container definitions for package building
* cmake targets for building packages
* initial gitlab CI + artifactory integration

Builds/containers/gitlab-ci/verify_head_commit.sh

@@ -0,0 +1,16 @@
+#!/usr/bin/env sh
+set -ex
+apt -y update
+apt -y install software-properties-common curl git gnupg
+curl -sk -o rippled-pubkeys.txt "${GIT_SIGN_PUBKEYS_URL}"
+gpg --import rippled-pubkeys.txt
+if git verify-commit HEAD; then
+    echo "git commit signature check passed"
+else
+    echo "git commit signature check failed"
+    git log -n 5 --color
+        --pretty=format:'%Cred%h%Creset -%C(yellow)%d%Creset %s %Cgreen(%cr) %C(bold blue)<%an> [%G?]%Creset'
+        --abbrev-commit
+    exit 1
+fi
+