MainPage.xaml.h/cpp: added OnVisibilityChanged handler & restarts video grabber
App.xaml.cpp: added debug stmts
window.cpp: changed HighguiBridge::getInstance() from get()
cap_winrt_video.h/cpp: changed HighguiBridge::getInstance() from get(), implemented closeGrabber()
cap_winrt_highgui.hpp: removed HighguiBridge_ prefix from enums
cap_winrt_highgui.cpp, cap_winrt.cpp, cap.cpp: implemented HighguiBridge::allocateOutputBuffer and getInstance() name change
main.cpp: changed slider action to change the color of the bar