IPv4 Default Route via Babel

[spolack]

Implements Step 3 of #964

[spolack]

The metrics for IPv4 (last commit on this PR) are already deployed on
ak36-gw
bht-core
emma-core
kiehlufer-core
l105-gw
magda-core
ohlauer-gw
philmel-core
rhnk-core
rhxb-core
saarbruecker-gw
sama-core
scharni-core
segen-core
simeon-core
strom-gw
vaterhaus-core
zwingli-core

to ensure most users can have a reasonable good experience with the change..

for i in *; do echo $i; scp -O $i/etc/bird.conf $i.olsr:/etc/; ssh root@$i.olsr /etc/init.d/bird restart; done

[Noki]

Also deployed this at:

agym-core
chris-core
dragonkiez-adlerhalle
dragonkiez-buero
dragonkiez-kiezraum
dragonkiez-rathausblock-miami
flughafen-core
funkigel
hirschhof-core
jup-core
k11-core
k12-h1-core
k12-h2-core
k12-h3-core
k12-h3-v0s
k12-h3-v2s
k12-h4-core
mela-core
rigaer78-core
rio-core
spitta13-core
teufelsberg-core
teufelssecurity-core
w38b-core
weidenbaum-core

[Noki]

looks good to me