Decapitalisation of copyright in 'Crown copyright'

Both the National Archives (http://www.nationalarchives.gov.uk/information-management/our-services/crown-copyright.htm) and the Copyright, Designs and Patents Act 1988 (http://www.legislation.gov.uk/ukpga/1988/48/section/163) refer to Crown copyright, not Crown Copyright.
Merge pull request #48 from bmwelby/patch-1

Decapitalisation of copyright in 'Crown copyright'