[Files Refactor] Import export fixup (#2763)

* Adjust json schema
* Remove mappings file from export
* Import file/folder support
* Update documentation
* Make gallery filenames unique

pkg/models/jsonschema/performer.go

@@ -40,6 +40,10 @@ type Performer struct {
 	IgnoreAutoTag bool             `json:"ignore_auto_tag,omitempty"`
 }
 
+func (s Performer) Filename() string {
+	return s.Name + ".json"
+}
+
 func LoadPerformerFile(filePath string) (*Performer, error) {
 	var performer Performer
 	file, err := os.Open(filePath)