more test cases, code refactoring and cleanup

...main/java/net/floodlightcontroller/firewall/Firewall.java

...a/net/floodlightcontroller/firewall/FirewallResource.java

.../java/net/floodlightcontroller/firewall/FirewallRule.java

.../floodlightcontroller/firewall/FirewallRulesResource.java

...et/floodlightcontroller/firewall/FirewallWebRoutable.java

...a/net/floodlightcontroller/firewall/IFirewallService.java

.../net/floodlightcontroller/firewall/RuleWildcardsPair.java

...java/net/floodlightcontroller/firewall/WildcardsPair.java

.../java/net/floodlightcontroller/firewall/FirewallTest.java