refs #5244 further modifications to allow ConvToMD running multithread

Code/Mantid/Framework/API/inc/MantidAPI/BoxController.h

Code/Mantid/Framework/Kernel/CMakeLists.txt

Code/Mantid/Framework/Kernel/inc/MantidKernel/FunctionTask.h

...k/MDAlgorithms/inc/MantidMDAlgorithms/ConvertToMDEvents.h

Code/Mantid/Framework/MDAlgorithms/src/ConvertToMDEvents.cpp

Code/Mantid/Framework/MDEvents/CMakeLists.txt

...ntid/Framework/MDEvents/inc/MantidMDEvents/ConvToMDBase.h

...work/MDEvents/inc/MantidMDEvents/ConvToMDEventsSelector.h

.../Framework/MDEvents/inc/MantidMDEvents/ConvToMDEventsWS.h

...ramework/MDEvents/inc/MantidMDEvents/ConvToMDPreprocDet.h

...ework/MDEvents/inc/MantidMDEvents/UnitsConversionHelper.h

Code/Mantid/Framework/MDEvents/src/ConvToMDBase.cpp

Code/Mantid/Framework/MDEvents/src/ConvToMDEventsHisto.cpp

.../Mantid/Framework/MDEvents/src/ConvToMDEventsSelector.cpp

Code/Mantid/Framework/MDEvents/src/ConvToMDEventsWS.cpp

Code/Mantid/Framework/MDEvents/src/ConvToMDPreprocDet.cpp

...ramework/MDEvents/src/ConvertToDiffractionMDWorkspace.cpp

Code/Mantid/Framework/MDEvents/src/MDEventWSWrapper.cpp

Code/Mantid/Framework/MDEvents/src/UnitsConversionHelper.cpp

...tid/Framework/MDEvents/test/ConvertToMDEventsParamsTest.h