Fix for link cost calculation into TopologyInstance for the metric "utilization". It was an erroneous copy-paste from the link-speed case.

Improve getPath() functions. Null is no longer returned anywhere. Instead, we use empty Path objects to indicate a path was not found.

Allow retrieval of VLAN tag from packet-in match. The VLAN tag might be here if the switch popped the VLAN tag from the packet itself prior to encapsulating it in the packet-in message.

Add new detailed-match property to define source and destination addresses to match on in each layer. Also add in-port as an optional match for the existing match property.

Don't use statistics service to get link speed. This can be derived from the IOSwitchService more efficiently. Remove link speed function from IStatisticsService.

Change log levels of frequent, unnecessary logs to debug. Were previously warn. Add new RoutingManager to properties

Restrict access to TopologyInstance constructor and compute() functions. Other public functions should also be changed to private or protected.