GOCB-235: Change Search query sorting order from descending to desc

Motivation
----------
A bug was reported by the community that field sort order
"descending" was wrong when sent to the server, and indeed
it needs to be "desc" on the wire.

Changes
-------
Updated the name used within search options to be desc rather
than descending.

Change-Id: I6062a99fa63c9f3af2ff18bbd4ee531d16e7d64e
Reviewed-on: http://review.couchbase.org/96506
Reviewed-by: Brett Lawson <brett19@gmail.com>
Tested-by: Charles Dixon <chvckd@gmail.com>

cbft/sorting.go

@@ -37,7 +37,7 @@ func NewSearchSortScore() *SearchSortScore {
 
 // Descending specifies the ordering of the results.
 func (q *SearchSortScore) Descending(descending bool) *SearchSortScore {
-	q.options["descending"] = descending
+	q.options["desc"] = descending
 	return q
 }
 
@@ -55,7 +55,7 @@ func NewSearchSortId() *SearchSortId {
 
 // Descending specifies the ordering of the results.
 func (q *SearchSortId) Descending(descending bool) *SearchSortId {
-	q.options["descending"] = descending
+	q.options["desc"] = descending
 	return q
 }
 
@@ -92,7 +92,7 @@ func (q *SearchSortField) Missing(missing string) *SearchSortField {
 
 // Descending specifies the ordering of the results.
 func (q *SearchSortField) Descending(descending bool) *SearchSortField {
-	q.options["descending"] = descending
+	q.options["desc"] = descending
 	return q
 }
 
@@ -118,6 +118,6 @@ func (q *SearchSortGeoDistance) Unit(unit string) *SearchSortGeoDistance {
 
 // Descending specifies the ordering of the results.
 func (q *SearchSortGeoDistance) Descending(descending bool) *SearchSortGeoDistance {
-	q.options["descending"] = descending
+	q.options["desc"] = descending
 	return q
 }