Finally LCD is done!!!
Another big change in this commit is that a custom GraphTraits class is
implmeneted. This enables us to extract all the cycle detection/collapse
codes into a single template base class, and HVN, HU,
OfflineCycleDetector and OnlineCycleDetector can all inherit from this
base class instead of writing their own cycle detection codes.
Finished HCD. Fixed several subtle yet critical bugs.
Also, the ptsGraph and constraintGraph are now updated online to save
more time/space