Allow public users to become temporary lexicographers through login

[kolatubosun]

We currently have people volunteer first before they can become lexicographers and work on the dictionary. For the next phase, have a "login" button on the homepage where public users can sign up (either through FB or Google or any other profile) and through which they can now leave feedback on entries more easily, or add new entries themselves, or edit current entries. As usual, their comment or edit or modification will not go live unless approved by volunteer lexicographers through the dashboard.