XCode Project Upgrade

Switching to XCTest
Enabling String ObjC_MsgSend
Update duplicate items

When an item already exists in keychain, the recommended procedures is
to update the existing item rather than delete the item and re-add it.
This preserves access control settings.
Authorization prompt for touchID / passcode

TouchID / Passcode UI supports a prompt explaining why the user is
being prompted for their password. This should be used whenever
retrieving values which were saved with the
kSecAttrAccessibleWhenPasscodeSetThisDeviceOnly accessibility level.
Merge branch 'TouchID-Keychain'