This allows DataList::create('SiteTree') as equivalent to Object::create('DataList', 'SiteTree'), without
having to have a create() function on DataList. Required for E_STRICT compliance.
API CHANGE: Deprecated SS_List::getRange() in favour of SS_Limitable::limit().
API CHANGE: Introduce SS_Limitable::limit($limit, $offset = 0) as the only modern way of specifying limits; deprecate all others.
API CHANGE: Simplified state handling so that it's just a key store. Affectors are replaced with GridField_ActionProviders. API CHANGE: Removed GridField state manipulation actions instead opting for GridField_ActionProvider actions.
API CHANGE: Removed support for modifiers that add "body" rows, instead having core support for generating the body rows hardcoded into the GridField.
API CHANGE: Allow modification of columns across the whole GridField with the GridField_ColumnProvider interface.
API CHANGE: Renamed GridField_AlterAction to GridField_Action, and added actionName/args parameters, since it can be used for all actions (including batch actions and row actions)
API CHANGE: Removed GridFieldRow class.
API CHANGE: Add DataList::newObject(), which creates a new object on that DataList.
API CHANGE: RequestHandler::handleRequest() now needs to handle a $model argument, if you override it.