Initial commit of boto_elb module and state.

This commit adds execution module and state module support for AWS ELBs. The
state module provides support for ensuring ELBs are absent or present. If present
the state will ensure health checks, listeners, availability zones, attributes,
and other ELB properties. The execution module adds support for all the necessary
actions in the state.
Use a dictionary for listeners rather than a list

Lists are difficult to properly sanity check and it's harder for the
end-user to use correctly.
Update docs for boto_elb listeners change
Remove debugging statement from boto_elb module
Fix docstring issue for boto_elb module
Merge pull request #12404 from lyft/boto-elb

Initial commit of boto_elb module and state.