[Mediawiki-i18n] Messages Text Change Suggestion

[Eugene Zelenko]

Hi!

During updating Belarusian translation I received suggestion to use
{{ns:Project}}: instead of Project:. I think will be good idea to make
same changes in Messages.php, which is used as base for translations.

In some messages wiki could be replaced with {{SITENAME}} (for example
in categoriespagetext)

With best regards,
Eugene.