add resources for generic, load-based, dynamic autoscaling to the existing `asg` module

[ketzacoatl]

Our existing asg module is a LC/ASG pair. After this update, the asg module would also include a set of resources to scale up/down the ASG. These resources are optional, and will be parametized.

Requirements

• Add the resources using the examples provided (in our other chat).
• Use modules from #195
• Parametize the critical CPU/scaling parameters (doesn't have to be all).

[Magicloud]

Seems like I just need move the calling to autoscaling-policy-metric-alarm-pair in load-asg example to asg module.

[Magicloud]

My design is kind hard to implement. If I give asg module a switch to turn on/off the autoscaling, and use count trick in the autoscaling module, it won't work because module does not support count yet.

Maybe we should merge the autoscaling-policy-metric-alarm-pair module into asg module?

[Magicloud]

Thinking about it, it is reasonable to combine the two modules, since the policy is meaningless without a group. But for user wants different metric, the builtin policy would be a burden, not too much.