Make tvb importers compatible with latest networkx version 2.0

2017-10-31 13:36:51,948 - INFO - tvb.core.services.flow_service - Starting operation CFF_Importer
2017-10-31 13:36:51,980 - ERROR - tvb.core.services.operation_service - Could not launch Operation with the given input data!
Traceback (most recent call last):
  File "c:\work\tvb\tvb-framework\tvb\core\services\operation_service.py", line 333, in initiate_prelaunch
    result_msg, nr_datatypes = adapter_instance._prelaunch(operation, unique_id, available_space, **params)
  File "c:\work\tvb\tvb-framework\tvb\adapters\uploaders\abcuploader.py", line 82, in _prelaunch
    return ABCSynchronous._prelaunch(self, operation, uid, available_disk_space, **kwargs)
  File "c:\work\tvb\tvb-framework\tvb\core\adapters\abcadapter.py", line 89, in new_function
    return func(*args, **kw)
  File "c:\work\tvb\tvb-framework\tvb\core\adapters\abcadapter.py", line 318, in _prelaunch
    result = self.launch(**kwargs)
  File "c:\work\tvb\tvb-framework\tvb\core\entities\storage\session_maker.py", line 344, in dec
    result = func(*args, **kwargs)
  File "c:\work\tvb\tvb-framework\tvb\adapters\uploaders\cff_importer.py", line 109, in launch
    partial = self._parse_connectome_network(network, warning_message, **kwargs)
  File "c:\work\tvb\tvb-framework\tvb\adapters\uploaders\cff_importer.py", line 145, in _parse_connectome_network
    connectivity = parser.parse(net.data)
  File "c:\work\tvb\tvb-framework\tvb\adapters\uploaders\networkx_connectivity\parser.py", line 110, in parse
    graph_size = len(network.nodes())
  File "C:\WORK\anaconda22\envs\tvb-clean\lib\site-packages\networkx\classes\graph.py", line 717, in nodes
    nodes = NodeView(self)
  File "C:\WORK\anaconda22\envs\tvb-clean\lib\site-packages\networkx\classes\reportviews.py", line 168, in __init__
    self._nodes = graph._node
AttributeError: 'Graph' object has no attribute '_node'