message: Avogadro io: remove unused jsoncpp linking
  The header file was also removed, as it is unused as well.
diff: @@ -15,7 +15,6 @@ endif()
  # compilers that support that notion.
  include_directories(SYSTEM "${EIGEN3_INCLUDE_DIR}"
  "${AvogadroLibs_SOURCE_DIR}/thirdparty/pugixml"
  - "${AvogadroLibs_SOURCE_DIR}/thirdparty/jsoncpp"
  "${AvogadroLibs_SOURCE_DIR}/thirdparty/struct"
  "${AvogadroLibs_SOURCE_DIR}/thirdparty")
  @@ -63,7 +62,7 @@ avogadro_add_library(AvogadroIO ${HEADERS} ${SOURCES})
  target_link_libraries(AvogadroIO
  LINK_PUBLIC AvogadroCore
  - LINK_PRIVATE jsoncpp struct)
  + LINK_PRIVATE struct)
  if(USE_HDF5)
  target_link_libraries(AvogadroIO LINK_PRIVATE ${HDF5_LIBRARIES})
  endif()
  