Add Android immersive mode switch function

Now to switch on immersive mode in Android the Qt's templates or code modification required. But this mode is mandatory needed for all game applications and not only. I request for new function in GUI Qt part - to turn on immersive mode (and other possible Android screen modes). The support must be implemented in QtActivity.java class. It requires modification of onCreate() and and onWindowFocusChanged() functions according to [this|https://forum.qt.io/topic/75789/max-screen-size-on-android-whithout-navigationbar-dimension/2.] And some AndroidManifest.XML tokens needed to turn immersive mode on.