Move get_seqs() to couch_set_view_util module

Change-Id: I697769a9bd5d62c358a44e19d16d1eda0437fb09
Reviewed-on: http://review.couchbase.org/38401
Reviewed-by: Volker Mische <volker.mische@gmail.com>
Tested-by: Sarath Lakshman <sarath@couchbase.com>