Add storage entity

entities/storage_entity.cpp

@@ -0,0 +1,21 @@
+#include "storage_entity.h"
+
+
+unsigned long long storage_entity::__global_id = 0;
+
+storage_entity::storage_entity(unsigned int capacity) : _capacity(capacity) {
+    this->_id = storage_entity::__global_id++;
+}
+
+
+unsigned long long storage_entity::id() {
+    return this->_id;
+}
+
+unsigned int storage_entity::capacity() {
+    return this->_capacity;
+}
+
+const QVector<cargo_entity> storage_entity::cargo() {
+    return this->_cargo;
+}