Fix coding conventions for sixlowpan and rpl module
Fix ieee802154_frame module
Decouple ICMPv6 from 6LoWPAN
Use net_if in 6LoWPAN MAC layer
Use net_if in 6LoWPAN layer
Let IPv6 and ICMP use new 6LoWPAN layer (+fixes)
Add sixlowpan to auto_init
Fix apps for previous changes