web/ProcessingQueue: use new types and states, refactor

- added a dedicated ui debug button
- fixed scrolling (content is no longer cutting off weirdly)
- moved stub to its own component
- moved all permanent strings to localization

web/i18n/en/button.json

@@ -16,5 +16,6 @@
     "save": "save",
     "export": "export",
     "yes": "yes",
-    "no": "no"
+    "no": "no",
+    "clear": "clear"
 }

web/i18n/en/queue.json

@@ -0,0 +1,6 @@
+{
+    "title": "processing queue",
+    "stub": "nothing in the queue yet, only two of us.\ntry {{ value }} something!",
+    "stub.download": "downloading",
+    "stub.remux": "remuxing"
+}