[TIMOB-7482] Ti.API: standardize children, parent and listeners properties

Request

It would be nice if "children", "parent" and "listeners" properties were standardized for all Titanium UI components. Currently, there is no way to traverse through whole tree of Titanium component in some context (window), or through some part of the tree. I don't know why "children" is removed from some components, but I think that's a bad idea (ok, maybe there is some valid technical reason that I don't know). Also, there is no way of knowing what event listeners where attached to particular component. "listeners" property existed once on Android (I think) but was removed. This properties should be read-only.

Current Behavior / Workaround

Currently, a workaround is to write JS wrappers for Titanium components, but for new developers that is disappointing fact because this features are basic features in some other environments. Unfortunately, there is no framework (for Titanium framework) available that does that (yet).