Fix CS buckets 2i query

This change makes sure that those always use pagination sort and fixes a
problem with start/end parameters after the refactor for the 1.4.4 2i
changes.  This uncovered some inconsistencies with the internal 2i query
parameters. This makes sure that bucket queries don't set start/end terms
and quality always have start=end and return_terms=false, among other
things. All 2i riak tests pass with this.
Merge pull request #759 from basho/bugfix/cs-buckets-2i-cleanup

Fix CS buckets 2i query