Rename fullscreen to maximize in next major release & add kiosk functions

[JustusFluegel]

the current setFullscreen works more like a .maximize() so I think we should call it that too. Behavour should be .maximize() = .toggleFullScreen() and .maximise(true) = .setFullScreen(true) and .maximize(false) = .setFullscreen(false). .isMaximized should be a getter for .getFullScreen();

the current fullcreen on Linux should be replaced with a maximize implementation and on macos .kioskMode(bool kioskMode) should do the same as maximize, but on Linux and Windows it should make the window fullscreen without any menu bars or the taskbar.

[seanocali]

Thankful someone tried to tackle this, but calling a maximized window 'fullscreen' is pretty farcical.