Doc updates
Doc updates

- added @warnings in UAirship for Appledoc

grosch/ios-library,jamesstout/ios-library_LITE,grosch/ios-library,zhangqinghe/ios-library,ipmobiletech/ios-library,mikerowan/ios-library,ipmobiletech/ios-library,manuyavuz/ios-library,zhangqinghe/ios-library,manuyavuz/ios-library,jamesstout/ios-library_LITE,jamesstout/ios-library_LITE,manuyavuz/ios-library,zhangqinghe/ios-library,ipmobiletech/ios-library,grosch/ios-library,mikerowan/ios-library,mikerowan/ios-library