##b-menu-horiz## blocks makes ##HTML## markup for a horizontal menu. The block
also has a functionality (implemented on JavaScript) that helps to write
scripts with reaction on a menu item becoming selected.

HTML markup complexity depends on a block modifier.

The block has ##layout## modifier with 3 following values:
 * ##horiz##
 * ##complex##
 * ##normal##

This block cannot be used without ##layout## modifier.