Pwh/st2cd

New additions
* add apt repo
* get apt repo gpg key
* run an st2 action remotely
* modified version of the st2_deploy.sh script to use the apt repo
* workflows for deployment and upgrade of st2
Hm, could we download this file from ops.stackstorm.net or something so we don't need to keep it in sync in two places (in st2 repo and here)?