Added some further clarification to the docs for Meta.managed.
Added some further clarification to the docs for Meta.managed.

Not sure if any of these are noticed as omissions yet; it's too new.
Primarily trying to head off questions in the future.

git-svn-id: 554f83ef17aa7291f84efa897c1acfc5d0035373@10107 bcc190cf-cafb-0310-a4f2-bffc1f526a37

svn2github/django,svn2github/django,svn2github/django