SDNNetwork model.

SDNNetworkModel contains SDNNetworkOFFlow.

SDNNetworkOFFlow represents a flow traversing the network following a path.
SDNNetworkOFFlow contains the Path it follows (from network model) and other OFFlow properties (SDNNetworkOFFlow extends OFFlow).

OFFlow has been created from FloodlightOFFlow, and FloodlightOFFlow changed to extend from OFFlow.
The difference between these two classes is that FloodlightOFFlow represents a flow entry inside a switch (and it holds the switch id),
while OFFlow is a generic flow representation.
Implement Bootstrapper that does not reset model.
Merge pull request #653 from isartcanyameres/feature/of-net-model

Feature/of net model