Until now (up to [iOS 9]), it was not possible to delete standard apps (it is possible to hide standard apps), but from [iOS 10] standard apps can be deleted like normal apps. can now be deleted (uninstalled).
Delete standard apps (uninstall)
Standard apps that can be removed
FaceTime iBooks iTunes Store Podcasts Watch Stocks Calendar Calculator Compass Weather Find Friends Videos Tips Home Voice Memos Maps Music Mail Notes Reminders Contacts …
Standard apps that cannot be deleted
App Store Find iPhone Safari Wallet Camera Settings Photos Phone Clock Health Messages …
