batman-adv: ELP - creating neighbor structures

Initially developed by Linus during a 6 months trainee study
period in Ascom (Switzerland) AG.

Signed-off-by: Linus Luessing <linus.luessing@web.de>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
Signed-off-by: Antonio Quartulli <antonio@open-mesh.com>