Add json save/write utilities

Tests implemented by @claude

Author: mmore500

Makefile

@@ -2,10 +2,11 @@
 TEST_DIR := source/catch
 EMP_DIR := Empirical/include
 SGP_DIR := signalgp-lite/include
+CEREAL_DIR := signalgp-lite/third-party/cereal/include
 
 # Flags to use regardless of compiler
 VENDORIZE_EMP_FLAGS := -DUIT_VENDORIZE_EMP -DUIT_SUPPRESS_MACRO_INSEEP_WARNINGS
-CFLAGS_all := -Wall -Wno-unused-function -std=c++20 -I$(EMP_DIR)/ -I$(SGP_DIR)/ ${VENDORIZE_EMP_FLAGS}
+CFLAGS_all := -Wall -Wno-unused-function -std=c++20 -I$(EMP_DIR)/ -I$(SGP_DIR)/ -I$(CEREAL_DIR)/ ${VENDORIZE_EMP_FLAGS}
 
 # Native compiler information
 CXX_nat := g++