Generate invite tokens from admin-fe

This MR allows to create invite tokens, list them on a separate tab, invite users via email. It also updates error handling and allows to generate tokens for resetting password.

Closes #28 (closed)

src/lang/en.js

@@ -317,6 +317,7 @@ export default {
     create: 'Create',
     revoke: 'Revoke',
     id: 'ID',
-    actions: 'Actions'
+    actions: 'Actions',
+    active: 'Active'
   }
 }