Panels.setIndex() can wrap around, if `wrap` is enabled

`enyo.Panels.setIndex()` can now respect values beyond the immediate scope of the current panel indexes, if `wrap: true` is present. Running `enyo.Panels.setIndex(-2)` will now set the index to the second-to-last panel on the `getPanels()` stack, if `wrap: true` is set. If not, it will simply set the index to 0 (zero), clamping, as it did previously.

Enyo-DCO-1.1-Signed-off-by: Blake Stephens <blake.stephens@lge.com>