[TIMOB-24839] Fix Ti.UI.Window object release

[garymathews]

• Do not fully release Titanium.UI.Window object onDestroy

TEST CASE

var a = Ti.UI.createWindow({backgroundColor: 'blue', title: 'Blue'}),
	b = Ti.UI.createWindow({backgroundColor: 'red', title: 'Red'});

a.addEventListener('click', function() {
	b.open();
	a.close();
});
b.addEventListener('click', function() {
	a.open();
	b.close();
});

a.open();

JIRA Ticket

[ypbnv]

CR: Pass

[lokeshchdhry]

FR Passed.

Opening a closed window does not crash the app.

1. Checked with the attached code.
2. Check it on tab group windows.

Studio Ver: 4.9.0.201705302345
SDK Ver: 6.2.0 local build
OS Ver: 10.12.3
Xcode Ver: Xcode 8.3.3
Appc NPM: 4.2.9
Appc CLI: 6.2.2
Ti CLI Ver: 5.0.14
Alloy Ver: 1.9.11
Node Ver: 6.10.1
Java Ver: 1.8.0_101
Devices: ⇨ google Pixel --- Android 7.1.1
⇨ google Nexus 5 --- Android 6.0.1