Modified UI to mention iPhone

Natural Locomotion

Move naturally in virtual reality in any SteamVR game that supports trackpad/stick locomotion. More immersion, more comfort!

Modified UI and help menu to mention iPhone, and include a link to the App Store. There's no functional change in this patch other than that, the iPhone app should have been working as-is. If you have trouble with the app and you have an old version of iOS, try updating it.