Fix up some comparators.

For RootsQuery and AllRootsQuery, we actually can't use TreeMultimap,
since that doesn't support "duplicate" key/value pairs, where duplicate
means where the key and value are equivalent (compare() == 0). So we do
need to just sort directly, after all.

I've also taken the opportunity to change ComparisonChain usages to
instead use Ordering.compound().
Upgrade Guava to 17.0, and switch Eclipse project to use Maven mode.
Use Arrays.stream(), not Arrays.asList().stream().
Merge branch 'master' into language-specific-histograms