Node related method and properties

VisuNodeNeighbours — node neighbours handling.
VisuNodeValues — generic way to store (and being notify) data for each node.
VisuNodeValuesFarray — define a VisuNodeValues object to handle any array of floats.
VisuNodeValuesString — define a VisuNodeValues object to handle strings.
VisuNodeValuesVector — define a VisuNodeValues object to handle vectorial node information.
VisuNodeValuesCoord — define a VisuNodeValues object to access node coordinates.
VisuNodeValuesType — define a VisuNodeValues object to access node typeinates.
VisuNodeValuesFrag — define a VisuNodeValues object to handle frags.
VisuNodeValuesShell — define a VisuNodeValues object to handle shells.
VisuNodeValuesId — define a VisuNodeValues object to access node idinates.