update plan comment summary to show changes

[neefrehman]

It would be great if the summary for the plan action would show the top-line changes, so the information could be more glanceable, like below:

53 to add, 155 to change, 53 to destroy.

FULL_PLAN_HERE

Or:

No changes. Infrastrcture up to date.

FULL_PLAN_HERE

This could be done by grepping the text for the right strings:

SUMMARY = grep -E '(to add|No changes)'