fixes some problems in the array-based nodes implementation
changess graph behavior for removing nodes (no more edges are removed)
adds degree distribution update for node removals (undirected only)
adds truncate methods for Object arrays
re-implements node removal in update correctly
renames diff to batch in multiple places
removes old datastructures (diff, metric, graph) and related classes
adds newNodeArray method to GraphDatastructures objects
adds invert method to DirectedEdge
adds DS to Nodes, fixes error in NodesA

- now, every Nodes Object also stores a pointer to a
GraphDatastructures object
- fixes an error in NodesA where the array was not shortened after the
last node is removed
adds some helper methods to ArrayUtils
removes Metric's cleanup() method
adds notion of neighbors and their storage to directed nodes
deletes old clustering coefficient implementations
adds new implementations of clustering coefficient computations
renames the new series implementation to 'Series'
renames the new metric implementation to 'Metric'