Batman adv netifd full integration

Since 2013.0.0 , slave interfaces are to be configured in /etc/config/network with proto=batadv,
but mesh parameters would still be set in /etc/config/batman-adv

With these changes, batX is also integrated into netifd framework, making it possible to configure the mesh parameters like this:

root@OpenWrt:~# head -n 4 /etc/config/network
config interface bat0
	option proto 'batmesh'
	option ifname 'bat0'
	option vis_mode 'server'

This completes the integration, so that netifd can properly setup and teardown interfaces as needed; no more issues when trying to /etc/init.d/network restart, everything comes up cleanly again
Also, openwrt packages files/ tree is much cleaner, with just 2 netifd proto scripts.