[Phantom] Phantom Settings Could Be Global if set

[Kenith]

Hello All,

We are using phantom to simulate iphone and pc to this site: http://detectmobilebrowsers.com/. However, if we set the phantomjs.page.settings.userAgent for iphone, the pc also uses the agent. Not expected.

For more info, please refer to Gemini_PhantomJS_SimulatePC&iPhone_Bug

Thank you, Ken