Reorginized the position of synch.h
Added ExpandedBlockStreamBase, which will provide stardard method for
expandable iterators.
ExpandableBlockStreamProjectionScan has been modified by using the
stardard methods provided by ExpandableBlockStreamIteratoBase. The code
is graceful now~ -_-
ExpandableBlockStreamFilter has been modifed by using the
ExpandableBlockStreamBase stardard methods. To be test the correctness.