rename engine.hpp/cpp to Engine.hpp/cpp & move Engine, Time and mainloop classes to 'engine' folder

src/PostRunnables.hpp

@@ -1,29 +0,0 @@
-#pragma once
-
-#include <queue>
-#include <mutex>
-#include "delegates.hpp"
-
-class PostRunnables {
-    std::queue<runnable> runnables;
-    std::recursive_mutex mutex;
-public:
-    void postRunnable(runnable task) {
-        std::lock_guard<std::recursive_mutex> lock(mutex);
-        runnables.push(std::move(task));
-    }
-
-    void run() {
-        std::queue<runnable> tasksToRun;
-        {
-            std::lock_guard<std::recursive_mutex> lock(mutex);
-            std::swap(tasksToRun, runnables);
-        }
-
-        while (!tasksToRun.empty()) {
-            auto& task = tasksToRun.front();
-            task();
-            tasksToRun.pop();
-        }
-    }
-};