BUGFIX When exporting data from TableListField to a CSV via TableListField_Item->Fields(), don't convert the values to XML
MINOR Added test class ConvertTest with tests for various Convert functions
git-svn-id: svn://svn.silverstripe.com/silverstripe/open/modules/sapphire/trunk@77298 467b73ca-7a2a-4603-9d3b-597d59a354a9