Core pr 5

Added reservation buttons (ajax) to the list.
Added import bookmarks.
Sure but - that would also be possible doing something like this:

```php
if (!user_is_logged_in()) {
  // Trigger log-in (the bookmark link will be triggered on success).
  $commands[] = ajax_command_ding_user_authenticate('');
} elseif (!ding_user_is_provider_user($user)) {
   ... more stuff
} elseif (!is_object($entity) || !($entity instanceof TingEntity)) {
   ... even more stuff
} else {
   ... finally we can do the real thing.
}
```