Fix shortcut conflict when one is a default (#1989)

* Fix config checking on startup

Signed-off-by: Haris Gušić <harisgusic.dev@gmail.com>

* Handle conflicts when one shortcut is a default

Signed-off-by: Haris Gušić <harisgusic.dev@gmail.com>

* Fix bugs

Signed-off-by: Haris Gušić <harisgusic.dev@gmail.com>

* Refactor slot in ShortcutsWidget for consistency

Signed-off-by: Haris Gušić <harisgusic.dev@gmail.com>

* Update shortcut table on config file change

Signed-off-by: Haris Gušić <harisgusic.dev@gmail.com>

* Fix bounded int bug in config

Signed-off-by: Haris Gušić <harisgusic.dev@gmail.com>

* Revert changes manually

Signed-off-by: Haris Gušić <harisgusic.dev@gmail.com>

* Reimplement ConfigHandler::shortcut and setShortcut

Signed-off-by: Haris Gušić <harisgusic.dev@gmail.com>

* Handle Return/Numpad-Enter equivalently

Signed-off-by: Haris Gušić <harisgusic.dev@gmail.com>

* Re-enable user-configured Imgur upload shortcut

Signed-off-by: Haris Gušić <harisgusic.dev@gmail.com>

* Document copyAndCloseAfterUpload config option

Signed-off-by: Haris Gušić <harisgusic.dev@gmail.com>

src/utils/valuehandler.h

@@ -153,9 +153,12 @@ public:
     bool check(const QVariant& val) override;
     QVariant fallback() override;
     QString expected() override;
+    QVariant representation(const QVariant& val) override;
 
 private:
     QKeySequence m_fallback;
+
+    QVariant process(const QVariant& val) override;
 };
 
 class ExistingDir : public ValueHandler