Replace "Modified" and "Published" yes/no columns with one coloured value
Replace "Modified" and "Published" yes/no columns with one coloured value

It is difficult to scan the current published/unpublished/modified columns.
This commit fixes that by combining the columns and using colour to
differentiate between the states.

tylerkidd/silverstripe-versioneddataobjects,glenn-bautista/silverstripe-versioneddataobjects,heyday/silverstripe-versioneddataobjects,tylerkidd/silverstripe-versioneddataobjects,heyday/silverstripe-versioneddataobjects,glenn-bautista/silverstripe-versioneddataobjects