'Register a sensor/device as available for serving of data through this XMPP
instance.
The device object may by any custom implementation to support
specific devices, but it must implement the functions:
has_field
request_fields
according to the interfaces shown in the example device.py file.
Arguments:
nodeId      -- The identifier for the device
device      -- The device object
commTimeout -- Time in seconds to wait between each callback from device during
a data readout. Float.
sourceId    -- [optional] identifying the data source controlling the device
cacheType   -- [optional] narrowing down the search to a specific kind of node'

def register_node(self, nodeId, device, commTimeout, sourceId=None, cacheType=None):

    self.nodes[nodeId] = {'device': device, 'commTimeout': commTimeout, 'sourceId': sourceId, 'cacheType': cacheType}
