Merge changes from topic 'bug/4218'

* changes:
  Bug 4218 - northbound: return 404 when deleting unexisting uuid
  northbound: introduce a base class for nortubhound classes

diff --cc northbound-api/src/main/java/org/opendaylight/neutron/northbound/api/NeutronFirewallNorthbound.java
Simple merge

diff --cc northbound-api/src/main/java/org/opendaylight/neutron/northbound/api/NeutronFirewallPolicyNorthbound.java
Simple merge

diff --cc northbound-api/src/main/java/org/opendaylight/neutron/northbound/api/NeutronFirewallRulesNorthbound.java
Simple merge

diff --cc northbound-api/src/main/java/org/opendaylight/neutron/northbound/api/NeutronFloatingIPsNorthbound.java
Simple merge

diff --cc northbound-api/src/main/java/org/opendaylight/neutron/northbound/api/NeutronLoadBalancerHealthMonitorNorthbound.java
Simple merge

diff --cc northbound-api/src/main/java/org/opendaylight/neutron/northbound/api/NeutronLoadBalancerListenerNorthbound.java
Simple merge

diff --cc northbound-api/src/main/java/org/opendaylight/neutron/northbound/api/NeutronLoadBalancerNorthbound.java
Simple merge

diff --cc northbound-api/src/main/java/org/opendaylight/neutron/northbound/api/NeutronLoadBalancerPoolNorthbound.java
Simple merge

diff --cc northbound-api/src/main/java/org/opendaylight/neutron/northbound/api/NeutronMeteringLabelsNorthbound.java
Simple merge

diff --cc northbound-api/src/main/java/org/opendaylight/neutron/northbound/api/NeutronSecurityGroupsNorthbound.java
Simple merge

diff --cc northbound-api/src/main/java/org/opendaylight/neutron/northbound/api/NeutronSecurityRulesNorthbound.java
Simple merge