Backup pack content and configs

[nmaludy]

@lenba from Slack asked if we could also backup the StackStorm pack content and pack configs currently installed on a machine.

I think this makes sense. We should also look into any other potential filesystem content that we need to backup, such as:

• /etc/st2/*
• /etc/mistral/*
• /etc/sysconfig/st2*
• /opt/stackstorm/chatops/st2chatops.env
• /opt/stackstorm/rbac
• /opt/stackstorm/virtualenvs (maybe?)
• RabbitMQ config?
• MongoDB config?
• Postgres config?
• nginx config?