Fixed #16371 -- Added a prefix "field-" to all CSS class names automatically...

Fixed #16371 -- Added a prefix "field-" to all CSS class names automatically generated from field names in admin forms to avoid conflicts with other common class names (e.g. "button"). This is backwards-incompatible for those who previously used plain field names as selector in custom style sheets or javascript transformations.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@16953 bcc190cf-cafb-0310-a4f2-bffc1f526a37