Allow passing objects to setOption('description')

[ne0-cz]

This is probably feature request but some might call it a bug :)

Same thing as #52 but for the Control description (which is translated in Renderer).

I'm using Kdyby\Translation: I'd like to be able to use Phrase (see https://forum.nette.org/cs/22010-kdyby-translation-validacni-message-formu-s-parametry): currently it's possible to use it only as label, not description.

I am running Nette 2.3 (because of Kdyby\Translation compatibility) but based on source code I think it's the same with 2.4:
https://api.nette.org/2.3/source-Forms.Rendering.DefaultFormRenderer.php.html#272
https://api.nette.org/2.4/source-Forms.Rendering.DefaultFormRenderer.php.html#277

I guess I can use Html as a workaround but then I'll end up with two different approaches for translatable strings with parameters depending on context (Control label vs Control description).

Currently the non-Html object is just being ignored: I can try making a PR but I'm afraid I'm not the right person - it makes no sense to me that label is translated in control and description in renderer: I am not really familiar with Forms source and therefore I might cause some horrible BC-break.

Or do you think that something like:

} elseif (is_object(($text) && $translator !== NULL) {
    $text = $translator->translate($text);
}

would be sufficient?

[ne0-cz]

Thank you!