ENH: Use RapidJSON instead of JsonCPP for performance improvement

RapidJSON is mganitudes faster than JsonCPP (https://github.com/miloyip/nativejson-benchmark).
This is important, because when terminologies (rather large json documents) are parsed/searched/modified then each operation may take hundreds of milliseconds
with JsonCPP. Multiple calls easily accumulate to user-perceivable delays (magnitude of seconds). By keep using JsonCPP we would constantly have to
optimize number of logic calls to make sure only json access is minimized. Also, JsonCPP was unbearably slow in debug mode in Windows (simple operations took
tens of seconds).

To minimize development time and optimize speed we switch to RapidJSON instead. RapidJSON's advantages compared to jsoncpp (https://github.com/miloyip/nativejson-benchmark):
* Magnitudes faster, also, its API facilitates writing efficient application code
* CMake-ified
* Header-only (no need to install DLLs, ...)
* More conform to json standard
* Library is much smaller (31k vs 243k)

CMake/SlicerGenerateSlicerConfig.cmake

@@ -126,7 +126,7 @@ set(Slicer_EP_COMPONENT_VARS_CONFIG
  "set(Slicer_VTK_COMPONENTS \"${Slicer_VTK_COMPONENTS}\")")
 
 # List all required external project
-set(Slicer_EXTERNAL_PROJECTS_CONFIG CTK ITK CURL Teem VTK)
+set(Slicer_EXTERNAL_PROJECTS_CONFIG CTK ITK CURL Teem VTK RapidJSON)
 set(Slicer_EXTERNAL_PROJECTS_NO_USEFILE_CONFIG CURL)
 if(Slicer_USE_QtTesting)
  list(APPEND Slicer_EXTERNAL_PROJECTS_CONFIG QtTesting)

CMakeLists.txt

@@ -293,14 +293,6 @@ mark_as_superbuild(Slicer_INSTALL_ITKPython)
 option(Slicer_BUILD_PARAMETERSERIALIZER_SUPPORT "Build Slicer with parameter serializer support" ON)
 mark_as_superbuild(Slicer_BUILD_PARAMETERSERIALIZER_SUPPORT)
 
-if(NOT Slicer_BUILD_PARAMETERSERIALIZER_SUPPORT)
- # Terminologies modules requires JSON, which is provided by parameter serializer.
- # Therefore, Slicer_BUILD_PARAMETERSERIALIZER_SUPPORT is required for Slicer build.
- # It could be possible to disable Terminologies module and all features that use it.
- message(FATAL_ERROR "Slicer_BUILD_PARAMETERSERIALIZER_SUPPORT option required to be enabled. ")
-endif()
-
-
 #
 # SimpleITK has large internal libraries, which take an extremely long
 # time to link on windows when they are static. Creating shared

Modules/Loadable/Terminologies/Logic/CMakeLists.txt

@@ -2,10 +2,12 @@ project(vtkSlicer${MODULE_NAME}ModuleLogic)
 
 set(KIT ${PROJECT_NAME})
 
+find_package(RapidJSON REQUIRED)
+
 set(${KIT}_EXPORT_DIRECTIVE "VTK_SLICER_${MODULE_NAME_UPPER}_LOGIC_EXPORT")
 
 set(${KIT}_INCLUDE_DIRECTORIES
- ${JsonCpp_INCLUDE_DIR}
+ ${RapidJSON_INCLUDE_DIR}
  )
 
 set(${KIT}_SRCS
@@ -20,7 +22,6 @@ set(${KIT}_SRCS
  )
 
 set(${KIT}_TARGET_LIBRARIES
- ${JsonCpp_LIBRARY}
  )
 
 #-----------------------------------------------------------------------------