Allow DataList::limit() to take a null value to remove the limit.
Added tests for limit(). Note the one failure, currently the ORM doesn't support unlimited values with an offset.
Remove all top/bottom margins from buttons and apply to GridFieldButtonRow component. Ensure that all buttons are added to a suitable GridFieldButtonRow in ModelAdmin, SecurityAdmin and Group.
Cleanup of framework's use of @package and @subpackage labels and additional of labels for classes missing packages.
Moved all GridField related components to the one name.
Countless spelling fixes, grammar for other comments.
Link ClassName references in file headers.
The entire framework repo (with the exception of system-generated files) has been amended to respect the 120c line-length limit. This is in preparation for the enforcement of this rule with PHP_CodeSniffer.
API CHANGE: Added GridField::getDataFieldValue() to encapsulate field lookup for all components.
API CHANGE: Allow 'callback' key to be specified in a GridFieldDataColumn column info. In this case, title should be put as the 'title' key of a map rather than simply the column info.
