Adding some more initial files

src/core/CMakeLists.txt

@@ -0,0 +1,9 @@
+
+set(CORE_HEADERS
+    entity.h
+)
+set(CORE_SOURCES
+    entity.cpp
+)
+
+add_library(core STATIC ${CORE_SOURCES})

src/core/entity.cpp

@@ -0,0 +1,6 @@
+#include "entity.h"
+
+Entity::Entity()
+{
+
+}

src/core/entity.h

@@ -0,0 +1,13 @@
+#ifndef ENTITY_H
+#define ENTITY_H
+
+class Entity
+{
+public:
+    Entity();
+    ~Entity();
+private:
+    int uuid{-1};
+};
+
+#endif //ENTITY_H