Re: referencing plugin javascript files

> Cache\InstalledPlugins\Plugins\SqueezeDSP\HTML\EN\plugins\SqueezeDSP\index.html

create another folder html below where you have index.html. Yes, it's 
awful, but the html (lowercase) sub folder would be served as static files.

> <script type="text/javascript" src="sqdsp_data.js"></script>

This then should become "html/sqdsp_data.js".