fix Date 'operation' Date foobar
fix Date 'operation' Date foobar

Post commit 9df90559d40f029479c4481e31f88737b70742f6 we have problems where Date types are added and subtracted. In fact that commit makes a subset of numberic operation return the date type. This fix ensures that the Date type is only applied when processing '+' ( old behaviour broken by the commit above ) and '-' ( new behaviour for consistency ) If both LHS & RHS are Date types then the result of the operations in question return the Double type.

JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core