Adds support for generating realistic looking UK landline and mobile phone numbers

Adds the options ukPhone and ukMobile to phone() method. Landline area codes for major cities and counties in the UK (including Scotland and Northern Ireland). Only 2, 3 and 4 digit area codes generated (excluding premium codes such as 08xx, 09xx) - http://en.wikipedia.org/wiki/Telephone_numbers_in_the_United_Kingdom#Four-digit_area_codes used as reference.