Move management of EF menu to base theme

• Move management of EF menu to base theme

We can't expect our projects to update their menu each time we decide to change our menu. The latest update in our hugo-solstice-theme now moves the menu management in the base theme. In the future, projects will automaticlly consume menu update by updating the theme sub-module.

Signed-off-by: Christopher Guindon chris.guindon@eclipse-foundation.org