Use TimeField and DateField instead of Time and Date

Time and Date is not documented and its name in ruby will colide with Time and
Date class.

to see its equal see
https://github.com/yast/yast-ycp-ui-bindings/blob/master/src/YCPDialogParser.cc#L317
and 
https://github.com/yast/yast-ycp-ui-bindings/blob/master/src/YCPDialogParser.cc#L329