syn_utilities.cxx fails to compile in that case as it doesn't know about include gadgetron_data_containers.h etc

I'm a bit confused about all this.

• If it's synergistic, then it should sit in Synergistic.
• In fact, this file include Syn/utilities.h, which defines the class ImageDataWrap but
  • a class declaration should ideally sit in a file with the name of the class.
  • the class implementation and declaration should be in the same folder structure
• seems that we need to have ImageWrap existing all the time (so in common I guess), but use preprocessor defines to exclude lines in syn_utilities.cpp that won't compile if an engine is not available.
• The CMakeListst.txt seems to imply that syn_utilities.ccp should only be compiled when all engines are present, which seems to be the opposite to what was intended
  

  SIRF/src/common/CMakeLists.txt

  Lines 30 to 45 in 6854699

  	if ((NOT DISABLE_STIR) AND (NOT DISABLE_Gadgetron) AND (NOT DISABLE_Registration) AND "${STIR_BUILT_WITH_ITK}")
  	MESSAGE(STATUS "Registration, ISMRMRD and STIR (with ITK) have been built.")
  	target_link_libraries(csirf PUBLIC iutilities csyn)
  	else()
  	MESSAGE(STATUS "Either Registration or ISMRMRD or STIR (with ITK) have not been built.")
  	add_library(Syn syn_utilities.cpp)
  	target_include_directories(Syn PUBLIC
  	"$<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}>$<INSTALL_INTERFACE:include>"
  	)
  	target_include_directories(Syn PUBLIC
  	"$<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>$<INSTALL_INTERFACE:include>"
  	)
  	target_link_libraries(Syn PUBLIC cgadgetron cstir Reg)
  	INSTALL(TARGETS Syn DESTINATION ${CMAKE_INSTALL_PREFIX}/lib)
  	target_link_libraries(csirf PUBLIC iutilities Syn)
  	endif()