Issue 893

Separates JS files into several priority groups. Then loads them in such order:
1. Global JS files (jQuery, jQuery UI, Fork CMS JS files and so on)
2. Default index is for custom module files added with $this->addJS inside module or widget
3. Modules JS files (Blog.js, Faq.js and module action files)
4. Widget JS files (CategoriesTree.js and so on)
This feature fixes IE9 and some other browsers loading order issue.