batman-adv: introduce capability initialization bitfield

The new bitfield allows us to keep track whether capability subsets of
an originator have gone through their initialization phase yet.

The translation table is the only user right now, but a new one will be
added soon.

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