#326539 by JohnAlbin, sun, cha0s, ultimateboy, Rob Loach, Damien Tournoud: Convert 'class' attribute to use an array, not a string.

#433992 by David_Rothstein and Frando: Change #theme_wrapper to #theme_wrappers to allow multiple theme functions to execute on renderable objects.

#306358 by dvessel, JohnAlbin, and flobruit: Add a single $classes string (and corresponding $classes_array) for all dynamic classes in template files.

#323112 follow-up by yched: Oops, Vertical Tabs broke field widgets (with tests so we don't do it again).

#369964 by yched and bjaspan: Refactor field validation and error reporting. Field API no longer coupled to Form API. Hooray.

- Patch #361683by Barry, Yves, Karen, Moshe Weitzman, David Strauss, floriant, chx, David Rothstein: initial field API patch. More work to be done, but ... oh my!