Babel and IPv6 integration

- Added babeld and radvd packages
- Added configuration files for babeld
- Added hotplug script for babeld
- Modified olsrd hotplug script to handle changing mesh protocol

Once built and installed, commands to change from Commotion to Babel:
1) uci set network.<meshName>.proto=babel (meshName is the value of 'uci show wireless.commotionMesh.network')
2) uci set wireless.commotionMesh.proto=babel
3) uci commit
4) /etc/init.d/network restart