Improved traversers

Added abstract class QueueBasedTraverser holds general logic for most
traversers.
Fixed errors in InfoKeepers.
Added InfoKeeper that uses IntToBoolean fastutil map to store Boolean
values.
Changed BreadthFirstTraverser so that first node is the node we start
traverse from (to be consistent with other traversals).
Could be, but this would make BoolInfoKeeper more complicated when it is not needed. I need to store underlying map from fastutils to have access to add method (that increases value given by a key) that is not available when I cast to java.util.Map.