Use ACTION_CHANGE_LIVE_WALLPAPER for the Set Wallpaper button.

[jjsil]

Also set the extra EXTRA_LIVE_WALLPAPER_COMPONENT so that a preview of the Meter wallpaper is shown directly instead of showing a list of all live wallpapers.

Tested on a Nexus 5X with Marshmallow and Google Now Launcher.

I haven't tested this on other launchers so I'm not sure how widespread support for ACTION_CHANGE_LIVE_WALLPAPER is or whether that's important :)