Autotag optimisation (#2368)

* Add duration to autotag finish message
* No sorting scene/image/gallery where not specified
* Use an LRU cache for sqlite regexp function
* Compile path separator regex once
* Cache objects with single letter first names
* Move finished auto-tag log
* Add more verbose logging
* Add new changelog

pkg/sqlite/studio.go

@@ -144,10 +144,6 @@ func (qb *studioQueryBuilder) QueryForAutoTag(words []string) ([]*models.Studio,
 	var whereClauses []string
 	var args []interface{}
 
-	// always include names that begin with a single character
-	whereClauses = append(whereClauses, "studios.name regexp ? OR COALESCE(studio_aliases.alias, '') regexp ?")
-	args = append(args, singleFirstCharacterRegex, singleFirstCharacterRegex)
-
 	for _, w := range words {
 		ww := w + "%"
 		whereClauses = append(whereClauses, "studios.name like ?")