Feature/ofertie ncl

Adds required components for the OFERTIE NCL (Network Controller Layer).

This pull request introduces two resource types:
- OpenFlow Switch (openflowswitch)
- SDN Network (sdnnetwork)
With capabilities and drivers to push flows into them.
OpenFlow enables switch devices are managed using floodlight v0.90 via the appropiated driver.

It also introduces the ofertie.ncl bundle providing the API and abstraction required to use components above in the context defined by OFERTIE project.

This pull request is associated with following OpenNaaS user stories:
http://jira.i2cat.net:8080/browse/OPENNAAS-1057
http://jira.i2cat.net:8080/browse/OPENNAAS-1060
http://jira.i2cat.net:8080/browse/OPENNAAS-1064