While the save password is not available, we do support Touch ID for iOS which provides similar functionality to a save password as the end user would only need to use Touch ID to login. For more information, please refer to KB40319.
Another possibilty is using certificate authentication. Pulse Workspace provides functionality to provision and push a certificate to all mobile devices, but this is possible with other MDM solutions as well. For more information about Pulse WorkSpace, please refer to KB40360.