Merge pull request #1868 from Bouke/tickets/18419

Fixed #18149 -- Changed language codes for Chinese
Improved changelog for runserver in 1.7.
Fixed python3 breakage introduced by c0a2388a1c4ead1afaec98e4ebc953a772ca3849.
Fixed admindocs injecting GenericSite string formatting and l10n

GenericSite's name could not be translated and showed it's __repr__ instead of
self.name in the template.