Tweaked and simplified the logic for the drawer activator image/icon property.
Uses the control's ID now, doesn't store the className supports more cases of icon/image and vice versa, the ability to reset it to defaults and have it update when either icon or src changes to both be blank, simplified generated CSS.

Enyo-DCO-1.1-Signed-off-by: Blake Stephens <blake.stephens@lge.com>