Add support for Json format input files (#118)

This change introduces a JSON parser and serializer for handling
input options. While the overall implementation is incomplete,
key functionality has been added.

Changes:
- Add nlohmann json to CMakeLists.txt
- Update to C++20
- Update CMake version as needed
- Add JsonParser for parsing a single options file
- Add JsonSerializer for serializing a single options file
- Refactor existing serialization to "LegacySerializer"
- Remove:
    cvDoubleVec jointXcoord
    cvDoubleVec jointYcoord
    cvDoubleVec jointZcoord
  from options (unused)
- Add "nodeAssociation" to joints list for explicit
  node associations in future updates

TODO:
- Add support for nested option files in JSON parser
- Add a converter for legacy format
- Update joint creation to use explicit node associations
- Update legacy parser to provide implicit node associations
  so they can be reused
- Verify changes against existing tests
- Add tests for parser, converter, etc.

Author: arsLibera

.gitignore

@@ -38,4 +38,6 @@ build
 .cproject
 .project
 .settings/
-.vscode/
+
+# Vscode
+.vscode/

CMakeLists.txt

@@ -111,6 +111,16 @@ if (BUILD_SV_INSTALLER)
     add_subdirectory("${CMAKE_SOURCE_DIR}/Distribution")
 ENDIF()
 
+# NLOHMANN JSON FOR SERIALIZATION
+include(FetchContent)
+FetchContent_Declare(
+    nlohmann_json
+    GIT_REPOSITORY https://github.com/nlohmann/json.git
+    GIT_TAG v3.11.2  # You can specify a version or use the latest tag
+)
+FetchContent_MakeAvailable(nlohmann_json)
+target_include_directories(${PROJECT_NAME} PUBLIC ${nlohmann_json_SOURCE_DIR}/single_include)
+
 # Unit tests and Google Test
 if(ENABLE_UNIT_TEST)
 
@@ -164,6 +174,13 @@ if(ENABLE_UNIT_TEST)
   # handle both use cases.
   target_link_libraries(UnitTestsExecutable gtest gtest_main pthread)
 
+  # We need to include Nlohmann when compiling the unit test executable
+  # A better strategy would be to build up a list of what we're going to
+  # include and reuse it.
+  # Another option: we could simply build the library of cvOneD functionality
+  # and link against that both here and in the main executable.  
+  target_include_directories(UnitTestsExecutable PRIVATE ${nlohmann_json_SOURCE_DIR}/single_include)
+
   # It's likely we'll need to include additional directories for some
   # versions of the unit tests. That can be updated when/if we update
   # the general strategy.