Do not try to replace window.navigator

[raphinesse]

window.navigator is a read-only property. Thus the current code for replacing it cannot succeed in a spec compliant browser. In strict mode the attempt will throw an error. In sloppy mode, the one Cordova is currently running in, the attempt is silently ignored.

Since apps seem to have been doing OK with the original Navigator object we should just remove the code trying to replace it.

[breautek]

In strict mode the attempt will throw an error.

After these changes, is using "use strict;" possible? I think with files that are strict mode friendly we should enable strict mode as it will allow the JS engines to enable optimisations that is otherwise impossible, and will prevent some bad practices being implemented in the future as well.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode

[raphinesse]

@breautek I'd be definitely in favor of enabling strict mode in the future. cordova-js should be strict mode ready after this change. But we need to proof the platforms too (since they are bundled into the same file as the base from cordova-js). There's at least one minor bug in cordova-android that will have to be fixed for this.