update copyright info

update license to GPLv2 and GPLv3

[pico_ethernet] - Added check for available headroom, and reallcation if there isn't enough headroom available

[IEEE802.15.4] - refactored

[pico_protocol] - Added 'device'-param to pico_protocol's alloc-function. This to alloc frames with overhead based on link layer and device's overhead-field. Should fix #405 and #376

Coverity ID 141541: ETH/ARP: Make sure frame is discarded in
pico_ethernet_receive on failure
This allows to remove the pico_discard_frame in pico_ethsend_local to
avoid a possible double free

[Ethernet] - Fixed heap-use-after-free and memory leak

[Ethernet] - comply to loop_score decrementing and added discartion on failure of enqueueing

[Ethernet] - Removed discartion when failed to determining link layer address

[Ethernet] - Updated comments about postponing and discarding

[Ethernet] - Return 1 on succes which is ret > 0w

[Ethernet] - Full PoC of seperation of ethernet in standalone protocols with its own queues and its own protocol definition.

Seperation of ethernet from the stack