Support custom navigation menu
With these changes, top navigation and bottom links will be customizable.
I'm working on this merge request for applying jekyll-kde-theme to jp.kde.org.
The custom top navigation is required becaise jp.kde.org is a bit larger. Because jp.kde.org has a lot of pages, too many links are shown in the navigation and the layout gets broken currently.
In regard to the custom bottom links, jp.kde.org needs links to the Japanese pages.