[WIP]
Migration of Muon LLP trigger classes to AthenaMT framework.
- Changed HTL::FexAlgo to AthAlgorithm and GetFeature/AttachFeature -> readHandle/WriteHandle in MuonClusterMT.cxx and MuonClusterMT.h
- Updated all instnces of HLT::OK to StatusCode::SUCCESS
Currently does not compile due to numerous outstanding errors.