userpage: use form langfile, move login strings to common

login-related stuff was moved into common using the langmover script, so
that the user page doesn't have to use the admin language files.

lang/setup/en-us.json

@@ -149,4 +149,4 @@
         "emailMessage": "Email Message",
         "emailMessageNotice": "Displays at the bottom of emails."
     }
-}
+}