API & Client - add API error messages translation

docs/api/auth.html

@@ -177,10 +177,10 @@
 <li><p>Sorry. That user already exists.</p></li>
 <li><dl class="simple">
 <dt>Errors:</dt><dd><ul>
-<li><p>Username: 3 to 12 characters required.</p></li>
+<li><p>3 to 12 characters required for usernanme.</p></li>
 <li><p>Valid email must be provided.</p></li>
 <li><p>Password and password confirmation don’t match.</p></li>
-<li><p>Password: 8 characters required.</p></li>
+<li><p>8 characters required for password.</p></li>
 </ul>
 </dd>
 </dl>