setup: report panic errors to user

many issues occur with setup, all this does is tell the user something
bad happened and to check the logs. Might help with solving issues.
Also fixed some now invalid typescript.

lang/setup/en-us.json

@@ -16,11 +16,13 @@
         "emailSubject": "Email Subject",
         "URL": "URL",
         "apiKey": "API Key",
+        "error": "Error",
         "errorInvalidUserPass": "Invalid username/password.",
         "errorNotAdmin": "User is not allowed to manage server.",
         "errorUserDisabled": "User may be disabled.",
         "error404": "404, check the internal URL.",
-        "errorConnectionRefused": "Connection refused."
+        "errorConnectionRefused": "Connection refused.",
+        "errorUnknown": "Unknown error, check app logs."
     },
     "startPage": {
         "welcome": "Welcome!",