/// Big_network
This class implements similar interface to TNGraph and TUNGraph.
The class is meant for storing particularly large static directed or undirected networks.
The network representation is optimized for low memory footprint.
This means that when a particular node is added to the network its (maximum) in- and out-degree need to be specified, so that the class allocates enough memory for that number of edges being adjacent to a node.
The class nicely supports adding as well as deleting nodes, although the memory does not get freed.
Deleting edges is supported, while adding edges is supported only up to the point until the node reaches its prespecified in- or out-degree.
///

/// TBigNet::TNode
For memory efficiency we store edge lists in a vector pool.
///

/// TBigNet::OutVId
If the graph is undirected (IsDir=false) then InVId==OutVId.
///

/// TBigNet::TNodeI
Only forward iteration (operator++) is supported.
///

/// TBigNet::TEdgeI
Only forward iteration (operator++) is supported.
///

