UI: Add functions for executing funcs without blocking

Adds functions for executing functions within separate threads without
blocking the user interface, or by blocking the user interface with a
dialog box.

UI/qt-wrappers.hpp

@@ -67,6 +67,12 @@ QDataStream &operator>>(QDataStream &in, OBSSceneItem &si);
 
 QThread *CreateQThread(std::function<void()> func);
 
+void ExecuteFuncSafeBlock(std::function<void()> func);
+void ExecuteFuncSafeBlockMsgBox(
+		std::function<void()> func,
+		const QString &title,
+		const QString &text);
+
 class SignalBlocker {
 	QWidget *widget;
 	bool blocked;