Implement simple echo request/reply
Set up new directory structure
Move error codes to public includes
Make sixlowpan module more coding conventions compliant
Add documentation group for 6LoWPAN module
Update documentation of ipv6.h
Document sixlowpan/error.h
Refactor mac.h
Make usage of IPHC configurable.
added callback registration for sixlowip
added callback for sixlowpan