IntegerSet and WrappedBitSetBitmap

Adeed IntegerSet
  * IntegerSet implements Set<Integer> and wraps any one of the MutableBitmap types
  * Updated the bitmap types to include a get(int) function to return if that bit is set

Added WrappedBitSetBitmap and WrappedImmutableBitSetBitMap
  * Wraps java.util.BitSet with ImmutableBitmap and MutableBitmap interfaces
compreTo in processing/src/main/java/io/druid/segment/data/BitmapCompressedIndexedInts.java returns which one is bigger. would that be desirable here?