Add elb create/delete, listener add/delete and health check commands

[bernd]

This adds sub commands for elb create/delete, elb listener add/delete and elb health check.

[ranjib]

awesome . $stdout.sync = true is needed? If we must need it, can you make it configurable. knife plugins can be re-used in other scripts, and in that case the consumer script might decide to control this behavior

thanks for the patch :-)

[bernd]

I copied the stdout.sync settings from the elb_list.rb. So no, it is not needed I guess. 😉 Removed!

[ranjib]

thank. i'll nuke it from the list code :-)

[bernd]

Great, thank you! 👍