adding handle single network method to the NetworkGeneralHelper;
moving getRealPriority to the NetworkGeneralHelper;
making priority constants part of the VirtualNetworkApplianceManager;
changing the network topology implementation in order to use the NetworkGeneralManager instead of the appliance
Conflicts:
server/src/com/cloud/network/router/VirtualNetworkApplianceManagerImpl.java
server/src/org/apache/cloudstack/network/topology/AdvancedNetworkTopology.java
server/src/org/apache/cloudstack/network/topology/BasicNetworkTopology.java