Update to use base localisation

This change removes the need to have multiple storyboard files by using Localisable.strings files and localising the text in the code.

Note - this does not use the built in iOS base localisation, as we want to keep support for iOS 5, so instead it follows the instructions provided in the link below.

http://techblog.41concepts.com/2012/08/06/a-critique-of-apples-approach-for-ios-gui-localization-and-how-to-do-it-much-better-in-your-apps/