Add method to present checkout preferences

• [ADDED] Provide method to let merchants change their checkout preferences
  +[SumupSDK presentCheckoutPreferencesFromViewController:animated:completion:]

Sample application:

• [ADDED] Add button to present checkout preferences
• [BUGFIX] Add missing -ObjC linker flag to Swift sample app

Support latest Air and Air Lite terminals

Important:
This release includes an updated certificate - Certificates included in any previous SDK version will expire Friday, 24th Feb 2017. Please make sure to update to this version until then.

• [IMPROVEMENT] Support latest Air and Air Lite terminals
• [IMPROVEMENT] Hosting app is no longer required to support any
  landscape device orientation on iPhone
• [IMPROVEMENT] Assert that SMPSharedResources is available when
  setting up SDK on simulator
• [ADDED] Includes upcoming SSL certificate - Certificates included in any previous SDK version will expire Friday, 24th Feb 2017
• [ADDED] Swift sample app

Layout improvements for iPhone 6, 6 Plus and iPad Pro

Deployment target changed to iOS 6.

• [UPDATE] Base SDK is iOS 9.3, deployment target is iOS 6
• [ADDED] Provide additional information on transaction and payment
  instrument in -[SMPCheckoutResult additionalInfo].
• [ADDED] New terminal including US support
• [BUGFIX] Fix an issue where some C&S transactions and mobile payments
  would incorrectly be reported as failed
• [IMPROVEMENT] Improve layout on iPhone 6, iPhone 6 Plus, and iPad Pro
• [IMPROVEMENT] Match style of SumUp iOS app version 1.60 and later
• [IMPROVEMENT] Improve support of Wake-on-Bluetooth PIN+ readers
• [IMPROVEMENT] Add nullability annotations
• [IMPROVEMENT] Prefix some internal classes to avoid duplicated symbols