fixes #2532134 in datatable sort

Fixed case sensitive sort order for string columns in datatable. Added test to cover data table containing Date, Number and String data types with case sensitive sort available by setting a caseSensitive param to true on the table column.

Setting a column with caseSensitive param to true e.g...

{key:"Company", label:"Sortable string (case sensitive)", sortable:true, caseSensitive:true} 

Will force case sensitive sorting, the default being case insensitive.