WIP: first take at qt_window player module

CMakeLists.txt

src/module/module_qt_window.c

src/module/qt_window/mpvwidget.cpp

src/module/qt_window/mpvwidget.hh

src/module/qt_window/mpvwidget_interface.cpp

src/module/qt_window/mpvwidget_interface.h

src/module/qt_window/qthelper.cpp