Copied "Norwegian Bokmål (nb)" translation to old "Norwegian (no)" translation...

Copied "Norwegian Bokmål (nb)" translation to old "Norwegian (no)" translation for backwards compatibility.

This change slightly extends what was decided in #11068 (to not update the "no" translation due to complicated maintenance, but only "nb"). Thanks, Transifex!

git-svn-id: http://code.djangoproject.com/svn/django/trunk@15887 bcc190cf-cafb-0310-a4f2-bffc1f526a37