Invalidate V8 DateTime cache on timezone changes

[darind]

Related to #961.

Added new flag handleTimeZoneChanges to app/package.json which invalidates V8 cache when the timezone is changed:

{
    "android": {
        "v8Flags": "--expose_gc",
        "handleTimeZoneChanges": true
    },
    "main": "app.js",
    "name": "tns-template-hello-world",
    "version": "4.0.0"
}

Because this functionality is not a common requirement for most apps, the default value for the flag is false.

[darind]

test