Add setting to keep screen on

[adstro]

Add a setting to keep the screen on while the app is running. I find this useful, so I thought others might as well.

[DDAZZA]

I think this is a good idea. I have a similar problem. However wouldn't want to keep my screen on all the time as I treasure my battery.

How about something like shaking the device to display the screen?

[adstro]

For my use case (which is what inspired the initial pull request), I leave my phone plugged in when using it to control XMBC.

I like your idea and it is not too hard to implement. I have written code to detect shaking before, and will add it to my repo and send a pull request.