Fixes for ENYO-3473, ENYO-3472

Updates and cleanup related to enyo.Model and enyo.Store. See https://enyojs.atlassian.net/browse/ENYO-3472, https://enyojs.atlassian.net/browse/ENYO-3473 for more information.

Enyo-DCO-1.1-Signed-off-by: Cole Davis <cole.davis@lge.com>