Updates for instance stats

[vsoch]

The first PR #784 is a base, and we will need to tweak and improve it! Currently this includes:

• Calculate % CPU
• Interactive monitoring with a loop that updates every n seconds, showing stats for more all instances

[dtrudg]

• Always start instances in a cgroup, where possible, to enable monitoring.

[vsoch]

@dtrudg I could work on this more if you want to spec out some details! Or something else, whatever is your preference.

[dtrudg]

@vsoch - apologies I've had some other urgent stuff to attend to the end of this week. I will get around to it next week.

[dtrudg]

I have replaced the step "Always start instances in a cgroup, where possible, to enable monitoring." with a full issue here:

#891

[dtrudg]

I have replaced the step "Interactive monitoring with a loop that updates every n seconds, showing stats for more all instances" with a full issue here:

#892

[dtrudg]

I have replaced the step "Calculate % CPU" with a full issue here:

#893

Closing this issue as it is now covered by the more detailed separate issues mentioned above.