Use RepoTags & RepoDigest in inspect

To be coherent with /images/json (images command)

Signed-off-by: Vincent Demeester <vincent@sbr.pm>

types/types.go

@@ -96,7 +96,8 @@ type GraphDriverData struct {
 // GET "/images/{name:.*}/json"
 type ImageInspect struct {
 	ID              string `json:"Id"`
-	Tags            []string
+	RepoTags        []string
+	RepoDigests     []string
 	Parent          string
 	Comment         string
 	Created         string