Add dev.md

[lumjjb]

Add a README to help developers

• build, test and lint check the code.
• notes on DCO and committing there.
• notes on common issues

[kdbeall]

Made a vagrant file. Would like to add this in a PR at some point.

Vagrant.configure("2") do |config|
  config.vm.box = "ubuntu/bionic64"
  config.vm.provider "virtualbox" do |v|
    v.memory = 2048
  end
  config.vm.provision "shell", inline: "apt update"
  config.vm.provision "shell", 
  inline: "apt -y install \
    apt-transport-https \
    ca-certificates \
    curl \
    gnupg-agent \
    software-properties-common"
  config.vm.provision "shell", inline: "apt-key adv --fetch-keys https://download.docker.com/linux/ubuntu/gpg"
  config.vm.provision "shell", 
  inline: "sudo add-apt-repository \"deb [arch=amd64] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable\""
  config.vm.provision "shell", inline: "apt update && apt -y install genisoimage jq docker-ce docker-ce-cli containerd.io golang-go go-dep libseccomp-dev python"
end