[LIBCLOUD-592] Create a generic method for listing AWS EIPs

Currently there are three methods in ec2 driver for listing EIPs:
They all satisfy different use cases:
ex_describe_all_addresses() - list all EIPs (vpc and ec2) optionally list only associated EIPs.
ex_describe_addresses() - list only EIPs for the specific nodes.
ex_describe_addresses_for_node() - list only EIPs for specific node.

This PR creates a generic method ex_list_addresses() to give users more flexibility while listing EIPs, by implementing all the functionality from this API call: http://docs.aws.amazon.com/AWSEC2/latest/APIReference/ApiReference-query-DescribeAddresses.html