JCLOUDS-99. Enable use of Iterable<IpPermission> for aws-ec2

- Added AWSEC2CreateSecurityGroupIfNeeded, using
AWSSecurityGroupClient's ability to call
authorizeSecurityGroupInRegion with Iterable<IpPermission>

- Added a utility method,
ComputeServiceUtils.getPortRangesInList(int... ports), to get pairs of
start/end ports covering all ranges in a list of ports. Used above.