Added format parameter

François,
I've added support for a *format* parameter to allow you to specify a format when the *sound* path is non-specific.

I was attempting to use WavPlayer to play WAV files in a helpdesk application (Spiceworks) that uses an obfuscated URL to link to attachments.  It did, however, have the real filename in the innerHTML of the anchor tag.  With this patch, I'm able to detect the file type in JS and then link to WavPlayer like this:

```
wavplayer.swf?gui=full&h=30&w=300&sound=/attachment/854&format=wav&
```

I did **not** update the WavPlayer JS interfaces such as DoPlay() to accommodate a format parameter.