Reduce dirty image pages by improving binning

Change ordering from dirty to less dirty since ArtFields are clean
and they are last. Add separate binning for DexCache and instances
of java lang object (probably a lock object).

Business card .art RAM (on shamu):
              PSS     Private Dirty
.art mmap     1011      600
.art mmap      990      560

Bug: 27906566

Change-Id: Ib3116953df7adafdc1560b064365c8b56e71483e