Merge pull request #587 from adrian-rosello/feature/vnmapper

Select network to map VNT request.
Added VNMapper to parent pom and features.
Helper methods and virtual-network-element classes in network model.
MapperResultParser to NetworkModel.
Integration test for VNMapping Capability.
Merge branch 'feature/vnmapper' of git://github.com/dana-i2cat/opennaas into feature/vnmapper
Name of virtual links removed.
Test for second example.
Errors in MappingResult fixed and tests for samples 3,4,.
Test for samples 5, 6
Network Model modified to add Virtualization support.
VNMapping tests 7 and 8.
NullPointer solved.