Rework sessions, remember cookies, and auth again

- Use Symfony's Session component to work with sessions, instead of a custom database model. Separate the concept of access tokens from sessions once again.
- Extract common session/remember cookie logic into SessionAuthenticator and Rememberer classes.
- Extract AuthenticateUserTrait into a new AuthenticationResponseFactory class.
- Fix forgot password process.

views/reset.blade.php

@@ -12,7 +12,8 @@
     <h1>Reset Your Password</h1>
 
     <form class="form-horizontal" role="form" method="POST" action="{{ app('Flarum\Forum\UrlGenerator')->toRoute('savePassword') }}">
-      <input type="hidden" name="token" value="{{ $token }}">
+      <input type="hidden" name="csrfToken" value="{{ $csrfToken }}">
+      <input type="hidden" name="passwordToken" value="{{ $passwordToken }}">
 
       <div class="form-group">
         <label class="control-label">Password</label>