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
@fjy We don't in particular need to use them, but some of them are simple enough I have a hard time warranting removing them.