[Owncloud] Use a UK English lang pack

[david at x2592.com]

Hi,

I wanted to customize the English used in ownCloud to UK English. So I 
went into the l10n folder of the site root, copied fr to en_GB, then 
worked on the .po files in poedit, being sure to set the language, 
country, etc. in the files.

But English (United Kingdom) doesn't show up in the list of languages in 
the Personal settings page.

Do I need to do something else to make ownCloud recognize the existence 
of UK English as opposed to the default English integrated into the 
software?

TIA for any pointers, and all the best, :-)

David