Add auto scrolling for containers

This is basically copy/paste work from the auto scrolling for text boxes. It adds the same feature for containers which would make my home screen in Xperience1080 a little bit easier because I could get rid of all the AlarmClocks and just add

```<autoscoll time="4000">Container(20).HasFocus(id)</autoscoll>```

to all the widgets.

I tested this a while ago and it worked fine but I couldn't get XBMC to build with Xcode 5 and OS X Mavericks so I haven't tested this recently. Maybe someone could have a look at this.

Thanks
`Black