Data repeater sample

This adds a simple data repeater sample, but also does a bit of modification to enyo.Collection and enyo.DataRepeater.  Note: enyo.DataList didn't seem to work for me before this, and it still doesn't work after this.

Let's chat about the changes... I think it's very important that DataRepeater work like the original enyo.Repeater, where it doesn't actually care if it's been rendered or not in its own code.