Merge branch 's3-mode' into 'master'

Add DataImportMode.S3

See merge request !1277

js/config.js

@@ -152,7 +152,8 @@ export const PROCESS_MODES = {
   iiif: 'IIIF',
   workers: 'Workers',
   transkribus: 'Transkribus',
-  template: 'Template'
+  template: 'Template',
+  s3: 'S3'
 }
 
 export const PROCESS_STATE_COLORS = {