ENYO-1025: Fix index issue in Collection.add() with purge: true
ENYO-1025: Fix index issue in Collection.add() with purge: true

The logic in VerticalDelegate to avoid unnecessary refreshes on
modelsAdded was being tripped up by an issue with Collection.add
in the case where the 'purge' option was set to true.

Specifically, the insertion index reported by Collection.add was
not properly adjusted in the case where models had been purged.

Enyo-DCO-1.1-Signed-Off-By: Gray Norton (gray.norton@lge.com)

PKRoma/enyo,beni55/enyo,wikieswan/enyo,wikieswan/enyo,soapdog/enyo,beni55/enyo,PKRoma/enyo,bright-sparks/enyo,soapdog/enyo,enyojs/enyo,kustomzone/enyo,bright-sparks/enyo,mcanthony/enyo,enyojs/enyo,kustomzone/enyo,mcanthony/enyo