Allow specifying the app bundle name

Our users started running into a problem where they would download the app several times and instead of running OurApp.app they'd run "OurApp 3.app" or something like that. In this situation we want the app to be moved to /Applications and renamed to OurApp.app. To this end we tweaked PFMoveToApplicationsFolderIfNecessary to allow specifying the desired app bundle name by setting a value for the PFDesiredAppBundleName key in Info.plist