new parameter and some bug fix

I've added the **widthMa**x parameter in order to fix a twig bug and make it configurable.

I've also modified the uploadify block to allow **multi-form retrieval of elements** using 
```javascript
$form.find("#...");
```
 instead of 
```javascript
$("#...");
```
 so that I can build many forms in the same page with (eventually) the same subelements id.