start work on invite keys

app/templates/common/topnav.html

@@ -21,7 +21,9 @@
     <input type="password" placeholder="Password" name="password" autocomplete="current-password" required>
     <span><input type="checkbox" name="remember" id="remember"> <label for="remember">Remember me</label></span>
     <input type="submit" value="Log in">
+    {%- if not config.DISABLE_SIGNUP -%}
     <a href="{{url_for('users.sign_up')}}" class="linkbutton alt">Sign up</a>
+    {%- endif -%}
   </form>
   {%- endif -%}
 </nav>