Fixed bug in SHMBuilder: readFile() should be static
SHMBuilder.segments(int) -> minSegments(int); Moved some logic from SHMBuilder to VanillaSHM (actually, there were two copies of the same logic: in SHMBuilder and VanillaSHM)
Extracted HashPosMultiMap interface from IntIntMultiMap and made package-private; IntIntMultiMap cleaned up