Huge improvements in Hawat web interface.

This patch introduces huge amount of work related to Hawat web interface. I was just clicking through the interface and trying to improve everything that popped out at the moment. There are following improvements:

* Enabled DataTable localication plugins.
* Implemented common layout for object management views (list views).
* Redesigned application menu implementation.
* Enhanced application menu to support contextual item action menus in listing tables. All administration list views now use it to generate contextual action toolbars.
* Menu object is now used even to generate breadcrumb menus.
* Simplified working with view icons and their propagation into action menus.
* Implemented AJAX spinner and used AJAX to fetch raw report data to web interface. There is stil a lot of room for improvements, the idea is for the user to be able to inteligently browse through the loaded data in some way.
* Redesigned object administration views (users, groups, filters, networks).
* Cleaned up list of built-in icons.
* Improved web interface translations after the changes in this commit.
* Fixed the bug in serving report data files.

(Redmine issue: #3734,#3443)