ENYO-403: Set selection state when setting multi-selection state.

### Issue
This is a sample-specific issue. Because we are binding `moon.ToggleButton` values to both the `selection` and `multipleSelection` properties, setting the `multipleSelection` property has no effect on the `selection` property.

### Fix
We add some logic to bind the states of the two buttons such that selection is enabled whenever multiple selection is enabled, but not vice versa.

Enyo-DCO-1.1-Signed-off-by: Aaron Tam <aaron.tam@lge.com>