Add delay mechanism for cordova nativeready event

This is needed for the pre-loaded webOS app container which
loads all the usual app libraries, including cordova, into
a hidden window, then loads app code into that window when
the user requests a launch.  The Cordova code needs to delay
running until the app is ready to start, so we need this
as a way of avoiding service bus calls before the container has
assumed the role of the requested app.

Enyo-DCO-1.1-Signed-Off-By: Ben Combee (ben.combee@lge.com)