JCLOUDS-661: Add ability to create single port firewall rule from Securi...

...tyGroupExtension

added check for to and from port being the same
added test in BaseSecurityGroupExtensionLiveTest

fixes https://issues.apache.org/jira/browse/JCLOUDS-661
[minor] I would be tempted to switch "from" and "to" ports in the comparison, because I tend to talk about ranges as "from X to Y", but that's just a personal preference - up to you.