Fixed some awkward wordings from docs/model-api.txt from [5519] and added 'new in Django development version' notes
Fixed some awkward wordings from docs/model-api.txt from [5519] and added 'new in Django development version' notes

git-svn-id: 4f9f921b081c523744c7bf24d959a0db39629563@5560 bcc190cf-cafb-0310-a4f2-bffc1f526a37

bfirsh/django-old,django-nonrel/django-nonrel,Smarsh/django,mitsuhiko/django,Instagram/django,sam-tsai/django-old,disqus/django-old,disqus/django-old,dcramer/django-compositepks,hugs/django,skevy/django,Instagram/django,bfirsh/django-old,sam-tsai/django-old,alex/django-old,hugs/django,Smarsh/django,bfirsh/django-old,jamespacileo/django-france,disqus/django-old,sam-tsai/django-old,django-nonrel/django-nonrel,dcramer/django-compositepks,dcramer/django-compositepks,mitsuhiko/django,skevy/django,jamespacileo/django-france,skevy/django,alex/django-old,jamespacileo/django-france,sam-tsai/django-old,alex/django-old,t11e/django,Instagram/django,Smarsh/django,django-nonrel/django-nonrel,mitsuhiko/django,t11e/django,t11e/django,Smarsh/django,hugs/django