o added sushi.py which combines Radiotap, MPDU parsing into one function bento
o changed RTAP.sz to RTAP.size for consistency
o restructured mpdu.py IOT alleviate cluttering of definitions, parsing helpers
etc in one file
- mpdu contains error, MPDU class and parse function
- moved public constants to file ieee80211.py
- moved private helper functions to _mpdu.py
o changed MPDU.info_els to MPDU.info_elements
o began parsing of all info_elements (see TODO for those not completed)
o modified getie, geties in mpdu
o info_elements in mgmt frames changed from list to dict
o added int2s - 2's complement to _mpdu