[ffulm] added hostname to the public ESSID.

Having the same ESSID for all nodes caused trouble because moving between nodes
does not seem to be possible with our setup (possibly due to luci_splash).
[ffulm] enforce ipv4 on batman

Not sure why this happened in the past but somehow v4 packets left through bat0
which froze the device for a few seconds.
Merge pull request #2 from saraedum/master

[ffulm] changes to increase stability