GF-12279: Add enyo.dom.addBodyClass method that defers settings any classes until ...

...app is rendered

Modify code that uses document.body to use this.

Enyo-DCO-1.1-Signed-Off-By: Ben Combee (ben.combee@lge.com)

For http://jira2.lgsvl.com/browse/GF-12279

Related: https://github.com/enyojs/enyo-ilib/pull/10