[android] Force an Android activity to always use landscape mode

Doing it in code is is IMO wrong and even more so if you put it into the onCreate. Do it in the manifest and the "system" knows the orientation from the startup of the app. And this type of meta or top level "guidance" SHOULD be in the manifest. If you want to prove it to yourself set a break in the Activity's onCreate. If you do it in code there it will be called twice : it starts up in Portrait mode then is switched to Landscape. This does not happen if you do it in the manifest.