packages/fff: Add fff-ra package

This Package adds a router advertisement daemon and
appropriate Freifunk Franken specific configuration for it.

The ra_default option is set to '2' to force the default flag,
even if no default route for ipv6 is present.
This is necessary, because otherwise fc00::/7 targets would be
unreachable, since odhcpd is unable to send specific routes inside a RA.
This won't affect clients ability to reach hosts which have a dual stack
connection, typical network stacks prefer IPv4 over IPv6 ULA when no
public IPv6 address is available.

Signed-off-by: Fabian Bläse <fabian@blaese.de>
Reviewed-by: Christian Dresel <fff@chrisi01.de>