- Adding StdOutLogger and adding tests for DAG execution to verify it works.

- Roughing in FileSystemLogger
- Deleting Scheduler code and associated unit tests as being too complicated for maintenance.
- Refactoring namespaces for loggers and executors.

cmake/MagicEnum.cmake

@@ -0,0 +1,17 @@
+include(ExternalProject)
+# Download RapidJSON
+ExternalProject_Add(
+        magic-enum
+        PREFIX "third_party/magic-enum"
+        GIT_REPOSITORY "https://github.com/Neargye/magic_enum"
+        GIT_TAG "v0.7.3"
+        TIMEOUT 10
+        CONFIGURE_COMMAND ""
+        BUILD_COMMAND ""
+        INSTALL_COMMAND ""
+        UPDATE_COMMAND ""
+)
+
+# Magic Enums is a header-only
+ExternalProject_Get_Property(magic-enum source_dir)
+set(MAGIC_ENUM_INCLUDE_DIR ${source_dir}/include)