Floodlight topology information retrieval to Topology Bridge

This commit contains the initial code that enables OSCARS's
Topology Bridge module to retrieve topology from Floodlight.
The code can be easily extended to incorporate information
from multiple SDN controllers. At the core are the
ISDNTopologyService interface, which defines what the
Topology Service should produce when the module requests
the topology and the BaseSDNTopologyService class, which
implements the singleton logic.

TODO:
Finish the code that exports the topology using XML
Fix maven dependencies for Jersey and Jackson libs
Add Jersey and Jackson jars to the repository
Adding two new mininet topologies to the repository (for testing).
Implementation of TopoBridge SDN REST input done.
Trying to figure out dependencies.

Saving current work
Making SDN PSS the default PSS
Adding some documentation to the method fetchDomainFromId of class TopologyCache
Improving documentation of ISDNTopologyService.

+ New method getDomainName(), that retrieves the domain name from a TopologyServiceIdentifier.
Moving SDNLink and SDNNode implementations from sdnPSS

These classes are of general use by any code that has some SDN logic.
Since TopoBridge is using them, I'm moving them to this module.

Methods to parse JSON-formatted links and to extract SDNNodes from a list
of links were also added in this commit.
Functional implementation of FloodlightSDNTopologyService

This commit changes the REST Library that was being used by
FloodlightSDNTopology service from Jersey to Restlet. The later
is simpler and cleaner than the former. This commit also contains
some bug fixes to BaseSDNTopologyService.java and the correct
dependency configuration for the module's maven project object
model.
Fixing the interfaces between TopoBridge original code and ISDNTopologyService.

All functionalities of TopoBridge module remains the same, except for domains
that have names starting with "sdn.". These will be fetched using ISDNTopologyService
according to SDNTopologyService controller-specific implementation. See
file net.es.oscars.topoBridge.sdn.ISDNTopologyService for more details.
Updating .gitignore (adding *.class to it)
Adding a example file on how to use Topology Bridge's FloodlightTopologyService.

Topology Bridge module's original functionality remains the same, except for
domains that have names starting with 'sdn.'. Those are fetched by
a SDN Controller-specific logic defined in net.es.oscars.topoBridge.sdn package.
For more information, check net.es.oscars.topoBridge.sdn.ISDNTopologyService.