Move creation of m_exp to a dummy module

library/FieldUtils/CMakeLists.txt

library/FieldUtils/InputModules/InputFld.cpp

library/FieldUtils/InputModules/InputXml.cpp

library/FieldUtils/ProcessModules/ProcessCreateExp.cpp

library/FieldUtils/ProcessModules/ProcessCreateExp.h

utilities/FieldConvert/FieldConvert.cpp