Radio: Moved numChannels parameter from radio medium to ieee80211 management module.
Radio: Removed obsolete ieee80211 radio medium C++ class.
Radio: Added common transmitter/receiver parameters to ieee80211 radio.
Radio: Merged ScalarRadio into Ieee80211Radio.

BTW, there was nothing scalar specific in ScalarRadio.
Radio: Followed recent renames around *RadioSignal*.
experimental