As a temporary solution I simply went to /sapphire/core/i18n.php and added the language/s I wanted and then commented all of the languages I did not need:
* A list of commonly used languages, in the form
* langcode => array( EnglishName, NativeName)
public static $common_languages = array(
'en' => array('English', 'English'),
'mi' => array('Maori', 'Māori')
/* deactivated languages for future reference
'af' => array('Afrikaans', 'Afrikaans'),
... etc ...
'zu' => array('Zulu', 'isiZulu')
This just leaves English and MÃ„Âori to toggle below the site tree and the translation tab only offers MÃ„Âori.
It seems to work well. However, this method means changing the core code. I was hoping to find a nicer way so I don't need to do this. Something like a setting for the _conf.php file, e.g. the imaginary methods:
i18n::setCommonLanguages = array('en' => array('English', 'English'));
or addCommonLanguages(), removeCommonLanguages() or removeAllCommonLanguages()
Maybe I just did not find it, but there was nothing obvious in the [url=http://api.silverstripe.com/]API[/url]. Or maybe it's just too late in the day :)
If you know of any better way please let me know.