Rename ProgressiveJob to SimpleJob

Because I had to.

src/frontend/helpers/simple_job.h

@@ -0,0 +1,37 @@
+// Copyright 2019 threeSD Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <functional>
+#include <QThread>
+#include "common/common_types.h"
+
+/**
+ * Lightweight wrapper around QThread, for easy use with progressive jobs.
+ */
+class SimpleJob : public QThread {
+    Q_OBJECT
+
+public:
+    using ProgressCallback = std::function<void(std::size_t, std::size_t)>;
+    using ExecuteFunc = std::function<bool(const ProgressCallback&)>;
+    using AbortFunc = std::function<void()>;
+
+    explicit SimpleJob(QObject* parent, ExecuteFunc execute, AbortFunc abort);
+    ~SimpleJob() override;
+
+    void run() override;
+    void Cancel();
+
+signals:
+    void ProgressUpdated(u64 current, u64 total);
+    void Completed();
+    void ErrorOccured();
+
+private:
+    ExecuteFunc execute;
+    AbortFunc abort;
+    bool canceled{};
+};