ChatOps commands

Originally proposed here https://github.com/StackStorm/discussions/issues/111 - find "Manual way (ChatOps)" paragraph.

In a long-term It's useful to have more ChatOps around the packages. Commands/statuses/web hooks.

For example, ability to start packages build directly from Slack. Command ideas:

!st2packages build v1.1
!st2packages build master on trusty
!st2packages build v1.3 on el7,el6

This will Trigger the new build where st2 staging box and CircleCI API are involved.

Nice thing will be to move all notifications and ChatOps around these builds in public #community channel, just behind RBAC. So we demonstrate the StackStorm ChatOps beauty and real use, possibly stimulate more interest from folks.

At the same time, there should be nicer report/notifications about result like:

• "New packages vX.Y.Z ... deployed, installation steps"
• "New Docker images vX.Y.Z... deployed, install HOWTO"

Overall more clear instructions, notifications and overall visbility and transparency about build/deploy process and final result. We can even post something to Twitter automatically (like new stable Docker containers vA.B.C are available).

Everything is up to discussion, but general idea: ChatOps would be useful.