1) Mving some functions to the a new class: CacheUtils.java
2) Some fixes in Graph.java, SmallGraph.java, DualSimulation.java, and
TightSimulation.java
3) TestHit.java
4) Some changes in query generators
In QueryGenerator, when it is intended to create subgraphs (degree==0),
the vertex IDs remain the same as the data graph; otherwise, they will
be normalized.