Multiple HTML Menu changes

* Added 'Model' category to addons list
* Fixed a bug with pages in main menu for saves and demos
* Switched some parts of the menu to the language system
* Saves now have Currently Popular section
* Saves now allow to browse through tags in main menu too
* Demos now have Currently Popular section too
* Re arranged buttons in Saves and Demos submenus in main menu to match
addons list