LayeredErrorModel: deleted.
ErrorModel: separated the layered and non-layered version.
Ieee80211LayeredErrorModel: followed recent changes.
Ieee80211LayeredReceiver: header fixes.
Ieee80211LayeredTransmitter: added a cautionary runtime error.
LayeredTransmission/LayeredScalarTransmission: added implementation.
Ieee80211LayeredDecoder: renamed to Ieee80211OFDMDecoder.
Phy: followed changes after renaming.