[SPARK-1977][MLLIB] register mutable BitSet in MovieLenseALS

Author: Neville Li <neville@spotify.com>

Closes #1319 from nevillelyh/gh/SPARK-1977 and squashes the following commits:

1f0a355 [Neville Li] [SPARK-1977][MLLIB] register mutable BitSet in MovieLenseALS

(cherry picked from commit f7ce1b3b48f0354434456241188c6a5d954852e2)
Signed-off-by: Xiangrui Meng <meng@databricks.com>