Update to ELB API to 2012-06-01 and add actions

This pull request updates the supported ELB API version to 2012-06-01, with minor parsing changes to account for changes in responses between the old and new API versions.

Support is added for the new(er) actions:

* ConfigureHealthCheck
* CreateLoadBalancerListeners
* DeleteLoadBalancerListeners

but this does not cover all the ELB actions available in 2012-06-01.

The changes were manually verified against Eucalyptus and AWS using the script:

https://gist.github.com/sjones4/a4fb910e99507cd3c300