Users of webOS and HTC Sense can skip ahead, you're already familiar with tight social networking integration on your handsets. Now Apple appears ready to join the social, so to speak. New evidence of low-level Facebook event and contacts integration has been revealed in iPhone OS 4 hinting at the possibility of unified Calendar and Contacts apps from Apple when the OS launches this summer on, um, this device. Web site Website Gunning for Safety says that Apple appears to have created a "separate type of contact" just for Facebook. On its own, the claim is suspect if only because the site's focus is related to nail gun safety. But we've grabbed copies of the associated .plist files from a